CompatHelper: bump compat for LinearSolve to 3, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the LinearSolve package from 2 to 2, 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 71.84%. Comparing base (5ba8097) to head (dc7bfcc).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #53   +/-   ##
=======================================
  Coverage   71.84%   71.84%           
=======================================
  Files          10       10           
  Lines         341      341           
=======================================
  Hits          245      245           
  Misses         96       96           

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