BUG: json_normalize() does not parse floats in scientific notation
- [x] I have checked that this issue has not already been reported.

- [x] I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---

**Note**: Please read [this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to provide the necessary information for us to reproduce your bug.

#### Code Sample, a copy-pastable example

```python
import json
import pandas as pd

body = '''[
{ "c1": 1, "c2": "1.01" },
{ "c1": 2, "c2": "1E-3" },
{ "c1": 3, "c2": "3.03" }
]'''

df1 = pd.read_json(body)
df2 = pd.json_normalize(json.loads(body))
print(df1, "\n\n", df1.dtypes)
print("\n\n", df2, "\n\n", df2.dtypes)
```

#### Problem description

When creating a dataframe from json string input via `json.loads()` and `pd.json_normalize()` float values in scientific notation (e.g. "1E-3") are not parsed as floats. When using `pd.read_json()` they are parsed correctly.

Output:
```
    c1     c2
0   1  1.010
1   2  0.001
2   3  3.030 

 c1      int64
c2    float64
dtype: object

    c1    c2
0   1  1.01
1   2  1E-3
2   3  3.03 

 c1     int64
c2    object
dtype: object
```

#### Expected Output

```
    c1     c2
0   1  1.010
1   2  0.001
2   3  3.030 

 c1      int64
c2    float64
dtype: object

    c1    c2
0   1  1.010
1   2  0.001
2   3  3.030

 c1      int64
c2    float64
dtype: object
```

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit           : 67a3d4241ab84419856b84fc3ebc9abcbe66c6b3
python           : 3.8.5.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.4.0-1019-gcp
Version          : #19-Ubuntu SMP Tue Jun 23 15:46:40 UTC 2020
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : en_US.UTF-8
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.1.4
numpy            : 1.19.4
pytz             : 2020.4
dateutil         : 2.8.1
pip              : 20.1.1
setuptools       : 47.1.0
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : None
html5lib         : 1.1
pymysql          : None
psycopg2         : None
jinja2           : 2.11.2
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fsspec           : None
fastparquet      : None
gcsfs            : None
matplotlib       : 3.3.1
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pytables         : None
pyxlsb           : None
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : 1.3.19
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
numba            : None

</details>
