feat: bump c7n and c7n-mailer to latest to support python3.9

[coxauto-kennyg]

Description

• bump c7n and c7n-mailer to latest to support python3.9

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[codecov-commenter]

Codecov Report

Merging #73 (586295d) into master (3696a27) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #73   +/-   ##
=======================================
  Coverage   61.49%   61.49%           
=======================================
  Files           9        9           
  Lines        1470     1470           
  Branches      306      306           
=======================================
  Hits          904      904           
  Misses        565      565           
  Partials        1        1           

Impacted Files	Coverage Δ
manheim_c7n_tools/version.py	100.00% <100.00%> (ø)

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