CompatHelper: bump compat for OrdinaryDiffEqLowStorageRK in [weakdeps] to 3, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the OrdinaryDiffEqLowStorageRK package from 1.15 to 1.15, 3.
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 89.02%. Comparing base (50d003f) to head (3a5ce32).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1177   +/-   ##
=======================================
  Coverage   89.02%   89.02%           
=======================================
  Files         128      128           
  Lines       10042    10042           
=======================================
  Hits         8940     8940           
  Misses       1102     1102           

Flag	Coverage Δ
total	89.02% <ø> (ø)
unit	68.09% <ø> (ø)

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