CompatHelper: bump compat for Ipopt to 0.9, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Ipopt package from 0.5, 0.6 to 0.5, 0.6, 0.9.
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

Merging #21 (161eed2) into master (82537d1) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #21   +/-   ##
=======================================
  Coverage   86.70%   86.70%           
=======================================
  Files           4        4           
  Lines         188      188           
=======================================
  Hits          163      163           
  Misses         25       25           

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