Actions: Add Python 3.10 and remove 3.5.

[methane]

No description provided.

[codecov]

Codecov Report

Merging #516 (62916b5) into main (16d139c) will increase coverage by 1.23%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #516      +/-   ##
==========================================
+ Coverage   85.79%   87.03%   +1.23%     
==========================================
  Files           6        6              
  Lines         542      586      +44     
==========================================
+ Hits          465      510      +45     
+ Misses         77       76       -1     

Impacted Files	Coverage Δ
MySQLdb/connections.py	90.85% <0.00%> (+3.83%)	⬆️

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