CompatHelper: bump compat for Flux in [weakdeps] to 0.16, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Flux package from v0.15.2 to v0.15.2, 0.16.
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 76.83%. Comparing base (4012634) to head (ce8dcf6).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #7      +/-   ##
==========================================
+ Coverage   75.47%   76.83%   +1.35%     
==========================================
  Files          16       18       +2     
  Lines         420      423       +3     
==========================================
+ Hits          317      325       +8     
+ Misses        103       98       -5     

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