Temporarily change tests to use 1.11

[mhauru]

Will open an issue to track the fact that this should be reverted ASAP once Mooncake and Libtask are back online.

[github-actions]

Turing.jl documentation for PR #2685 is available at:
https://TuringLang.github.io/Turing.jl/previews/PR2685/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.21%. Comparing base (d8fbe78) to head (2a1037c).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2685   +/-   ##
=======================================
  Coverage   87.21%   87.21%           
=======================================
  Files          22       22           
  Lines        1431     1431           
=======================================
  Hits         1248     1248           
  Misses        183      183           

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[sunxd3]

I don't have major issue. But since we know that 1.12 is going to fail, should we just skip it altogether for now? (I am also not sure why some CIs seem to stuck.)