chore: update dependencies

[jansegre]

Test run of docker CI updates: https://github.com/jansegre/hathor-core/runs/6309343035?check_suite_focus=true

Together with the updating of the dependencies is making the fixes necessary for the updated linters and also updating the PyPy images to 3.8 and 3.9 (with PyPy 3.7 removed). We can now start dropping support for Python 3.7 if we want to.

[codecov]

Codecov Report

Merging #404 (42a21c7) into dev (5cf270c) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev     #404      +/-   ##
==========================================
+ Coverage   82.83%   82.84%   +0.01%     
==========================================
  Files         171      171              
  Lines       15585    15585              
  Branches     2466     2466              
==========================================
+ Hits        12910    12912       +2     
+ Misses       2228     2226       -2     
  Partials      447      447              

Impacted Files	Coverage Δ
hathor/merged_mining/coordinator.py	42.85% <100.00%> (+0.41%)	⬆️
hathor/indexes/manager.py	92.85% <0.00%> (-0.90%)	⬇️
hathor/p2p/node_sync.py	83.53% <0.00%> (ø)

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