Skip Mooncake on 1.12

[penelopeysm]

1.12 isn't being tested right now on Turing, so this doesn't actually affect anything here; but DynamicPPL's integration test uses 1.12 and it seems unfair to pin that to 1.11 when most of Turing's test suite should pass on 1.12.

[github-actions]

Turing.jl documentation for PR #2705 is available at:
https://TuringLang.github.io/Turing.jl/previews/PR2705/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.45%. Comparing base (5ceb7e6) to head (e54ba56).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2705   +/-   ##
=======================================
  Coverage   86.45%   86.45%           
=======================================
  Files          21       21           
  Lines        1418     1418           
=======================================
  Hits         1226     1226           
  Misses        192      192           

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