CompatHelper: bump compat for GradedArrays in [weakdeps] to 0.15, (keep existing compat)

[ITensorBot]

This pull request changes the compat entry for the GradedArrays package from 0.14.6 to 0.14.6, 0.15.
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 77.92%. Comparing base (4a3c1ed) to head (fec56d6).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #237   +/-   ##
=======================================
  Coverage   77.92%   77.92%           
=======================================
  Files          30       30           
  Lines        1803     1803           
=======================================
  Hits         1405     1405           
  Misses        398      398           

Flag	Coverage Δ
docs	26.36% <ø> (ø)

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