Use shared auto-milestone workflow

[douglatornell]

Replace the custom milestone action with the shared workflow from UBC-MOAD. This simplifies maintenance and ensures consistency across repositories.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 53.69%. Comparing base (b53b98d) to head (5c8a84b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #133   +/-   ##
=======================================
  Coverage   53.69%   53.69%           
=======================================
  Files          29       29           
  Lines        3531     3531           
=======================================
  Hits         1896     1896           
  Misses       1635     1635           

Flag	Coverage Δ
unittests	53.69% <ø> (ø)

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