CompatHelper: bump compat for StructArrays to 0.7, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the StructArrays package from 0.6.15 to 0.6.15, 0.7.
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 92.46%. Comparing base (c55ea63) to head (690409e).
Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #292   +/-   ##
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  Coverage   92.46%   92.46%           
=======================================
  Files           7        7           
  Lines         385      385           
=======================================
  Hits          356      356           
  Misses         29       29           

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