pin mysqlclient to prevent dependency failures

[mbordash2]

Summary

GHA failing due to dependency needs of the mysqlclient.

Why This Is Needed

PyMySQL/mysqlclient#620

What Changed

Pinning mysql client to a version that doesn't have new dependencies required.

Checklist

• Have you followed the guidelines in our Contribution Requirements?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Does your submission pass tests?
• Have you linted your code locally prior to submission?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?
• Have you updated documentation, as applicable?

[codecov]

Codecov Report

Merging #1938 (4c51628) into master (230ccf5) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1938   +/-   ##
=======================================
  Coverage   90.17%   90.17%           
=======================================
  Files         247      247           
  Lines       15667    15667           
=======================================
  Hits        14128    14128           
  Misses       1539     1539           

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