TST: Check float format in object column (#35603)
- [ ] closes #35603
- [x] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

This test checks if a Series cast to object still shows data in float format.

Ran `pytest pandas/tests/series/test_constructors.py`
Output:
```
================================================= test session starts =================================================
platform win32 -- Python 3.8.10, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: C:\Users\mdhsi\pandas-michael, configfile: pyproject.toml
plugins: hypothesis-6.12.0, asyncio-0.14.0, cov-2.11.1, forked-1.3.0, instafail-0.4.1, xdist-2.2.1
collected 301 items

pandas\tests\series\test_constructors.py .......................................................................................................................................................................................................x.....................................................................................................

--------------------------- generated xml file: C:\Users\mdhsi\pandas-michael\test-data.xml ---------------------------
================================================ slowest 30 durations =================================================
0.25s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_empty_constructor[<lambda>-True0]
0.13s call     pandas/tests/series/test_constructors.py::TestSeriesConstructorIndexCoercion::test_series_constructor_datetimelike_index_coercion
0.09s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['dateutil/US/Pacific'-True]
0.04s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_dtype_datetime64_10
0.02s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_empty[OrderedDict]
0.02s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_empty[dict]
0.02s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_cant_cast_datetimelike[PeriodIndex]
0.02s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_cant_cast_datetimelike[DatetimeIndex]
0.02s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_cant_cast_datetimelike[TimedeltaIndex]
0.02s setup    pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_datetimelike_scalar_to_string_dtype[string]
0.02s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_pass_none
0.02s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_categorical_with_coercion
0.02s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_dtype_timedelta64
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive[pytz.FixedOffset(300)-False]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['Asia/Tokyo'-True]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive[pytz.FixedOffset(300)-True]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive[tzlocal()-False]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['dateutil/Asia/Singapore'-False]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive[datetime.timezone(datetime.timedelta(seconds=3600))-False]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive[tzutc()-False]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['+01:15'-True]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['UTC'-False]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['UTC-02:15'-True]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive[tzlocal()-True]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive[pytz.FixedOffset(-300)-True]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['dateutil/Asia/Singapore'-True]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['UTC'-True]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive['-02:15'-False]
0.01s call     pandas/tests/series/test_constructors.py::TestSeriesConstructors::test_constructor_data_aware_dtype_naive[pytz.FixedOffset(-300)-False]
=========================================== 300 passed, 1 xfailed in 2.22s ============================================
```