Import ABC from collections.abc for Python 3.10 compatibility.

[tirkarthi]

The justification for this PR is:

Importing ABC from collections was deprecated since Python 3.4 and removed in Python 3.10 . Use collections.abc instead.

[codecov]

Codecov Report

Merging #150 (a657d04) into main (e849359) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #150   +/-   ##
=======================================
  Coverage   86.05%   86.05%           
=======================================
  Files          18       18           
  Lines        1226     1226           
=======================================
  Hits         1055     1055           
  Misses        171      171           

Impacted Files	Coverage Δ
splot/_viz_value_by_alpha_mpl.py	96.09% <100.00%> (ø)

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[martinfleis]

Thanks