[CLIENT-2405] Remove Python 3.7 support

[juliannguyen4]

Build wheels works without Python 3.7 builds: https://github.com/aerospike/aerospike-client-python/actions/runs/6227882087
Valgrind runs upgraded to Python 3.8: https://github.com/aerospike/aerospike-client-python/actions/runs/6227792889/job/16903184447

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (39d0759) 81.30% compared to head (8c4a2f9) 81.30%.

Additional details and impacted files

@@           Coverage Diff           @@
##            stage     #510   +/-   ##
=======================================
  Coverage   81.30%   81.30%           
=======================================
  Files          98       98           
  Lines       14808    14808           
=======================================
  Hits        12039    12039           
  Misses       2769     2769           

Files Changed	Coverage Δ
src/main/aerospike.c	85.86% <100.00%> (ø)

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[justinlee-aerospike]

changes look good