CompatHelper: bump compat for SUNRepresentations in [weakdeps] to 0.4, (keep existing compat)

[mtfishman]

This pull request changes the compat entry for the SUNRepresentations package from 0.3 to 0.3, 0.4.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.18%. Comparing base (f42183a) to head (d9066c3).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #156   +/-   ##
=======================================
  Coverage   87.18%   87.18%           
=======================================
  Files          20       20           
  Lines        1264     1264           
=======================================
  Hits         1102     1102           
  Misses        162      162           

Flag	Coverage Δ
docs	0.00% <ø> (ø)

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