Regenerated Excel files to Suppress Openpyxl Warnings
As noticed by @jorisvandenbossche openpyxl was throwing some warnings for excel files in the test suite. The warnings did not appear relevant to the data within the files and are most likely historical artifacts of how  the files were created. Simply resaving these removes the warning from the builds

```sh
pandas/tests/io/excel/test_readers.py::TestReaders::test_reader_special_dtypes[openpyxl-.xlsx]
pandas/tests/io/excel/test_readers.py::TestReaders::test_reader_special_dtypes[openpyxl-.xlsm]
pandas/tests/io/excel/test_readers.py::TestReaders::test_reading_all_sheets[openpyxl-.xlsx]
pandas/tests/io/excel/test_readers.py::TestReaders::test_reading_all_sheets[openpyxl-.xlsm]
pandas/tests/io/excel/test_readers.py::TestReaders::test_reading_multiple_specific_sheets[openpyxl-.xlsx]
pandas/tests/io/excel/test_readers.py::TestReaders::test_reading_multiple_specific_sheets[openpyxl-.xlsm]
pandas/tests/io/excel/test_readers.py::TestReaders::test_read_excel_squeeze[openpyxl-.xlsx]
pandas/tests/io/excel/test_readers.py::TestReaders::test_read_excel_squeeze[openpyxl-.xlsm]
pandas/tests/io/excel/test_readers.py::TestExcelFileRead::test_excel_passes_na[openpyxl-.xlsx]
pandas/tests/io/excel/test_readers.py::TestExcelFileRead::test_excel_passes_na[openpyxl-.xlsm]
  /Users/williamayd/miniconda3/envs/pandas-dev/lib/python3.7/site-packages/openpyxl/worksheet/_reader.py:296: UserWarning: Unknown extension is not supported and will be removed
```