Bump version and update change log for 1.4.12

[junkmd]

As stated in #848 (comment), this will be the final release supporting Python 3.8.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.74%. Comparing base (5c564ec) to head (51d2497).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #872      +/-   ##
==========================================
+ Coverage   84.72%   84.74%   +0.02%     
==========================================
  Files         125      125              
  Lines       11566    11566              
==========================================
+ Hits         9799     9802       +3     
+ Misses       1767     1764       -3     

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