clean up warnings in tests

[melange396]

deprecation warnings are artifacts from doing version updates, its best to fix these before they stop being warnings and become errors. the current warnings output is:

=============================== warnings summary ===============================
repos/delphi/delphi-epidata/integrations/acquisition/covidcast/test_csv_uploading.py::CsvUploadingTests::test_uploading
  /usr/local/lib/python3.8/site-packages/pandas/core/indexing.py:1637: SettingWithCopyWarning:
  A value is trying to be set on a copy of a slice from a DataFrame

  See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
    self._setitem_single_block(indexer, value, name)

repos/delphi/delphi-epidata/integrations/acquisition/covidcast_nowcast/test_csv_uploading.py::CsvUploadingTests::test_duplicate_row
repos/delphi/delphi-epidata/integrations/acquisition/covidcast_nowcast/test_csv_uploading.py::CsvUploadingTests::test_duplicate_row
repos/delphi/delphi-epidata/integrations/acquisition/covidcast_nowcast/test_csv_uploading.py::CsvUploadingTests::test_uploading
  /usr/local/lib/python3.8/site-packages/pandas/io/sql.py:1429: SADeprecationWarning: The Engine.run_callable() method is deprecated and will be removed in a future release.  Use the Engine.begin() context manager instead. (deprecated since: 1.4)
    return self.connectable.run_callable(

[dshemetov]

Bumping up to pandas==1.2.4 removes these warnings.