CompatHelper: bump compat for Turing in [weakdeps] to 0.42, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the Turing package from 0.39 to 0.39, 0.42.
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.

[github-actions]

TuringCallbacks.jl documentation for PR #67 is available at:
https://TuringLang.github.io/TuringCallbacks.jl/previews/PR67/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.76%. Comparing base (999bd3c) to head (a8d7ed2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #67      +/-   ##
==========================================
- Coverage   61.58%   59.76%   -1.82%     
==========================================
  Files           7        7              
  Lines         177      169       -8     
==========================================
- Hits          109      101       -8     
  Misses         68       68              

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