Revert "Update codecov/codecov-action action to v4"

[cakebaker]

Reverts #57 because they tagged the version prematurely, see codecov/codecov-action#1089

[codecov]

Codecov Report

Merging #58 (14ee0ad) into main (8929988) will not change coverage.
Report is 2 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #58   +/-   ##
=======================================
  Coverage   94.97%   94.97%           
=======================================
  Files           4        4           
  Lines         956      956           
=======================================
  Hits          908      908           
  Misses         48       48           

Flag	Coverage Δ
macos_latest	99.32% <0.00%> (ø)
ubuntu_latest	99.33% <0.00%> (ø)
windows_latest	94.48% <0.00%> (ø)

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