Replace deprecated UQ() with !! operator (#457)

[ishaan-arora-1]

Replaces all 11 deprecated UQ() calls with !! across mcmc-parcoord.R, mcmc-scatterplots.R, and mcmc-traces.R.

Reference: https://rlang.r-lib.org/reference/UQ.html

Closes #457

[ishaan-arora-1]

@jgabry the 16 vdiff snapshot failure are unrelated to this pr. they are caused by R 4.5.3 producing slightly diff rendering that 4.5.2. the same failures appear on other prs which run tests after the update.
ive made the changes required to it in pr #430. id suggest you check that out.

[jgabry]

Thanks, yeah I actually have a separate PR open for updating the snapshots for R 4.5.3. I think we should handle that separate from these more specific PRs and then merge master into these branches. That is, I don't want to wait to update the SVGs until we merge #430 because #430 includes other changes that need to be reviewed, whereas the SVG update should happen now and then all the PR branches should be updated. The SVG PR is #460, which I'll merge as soon as tests pass and then we can update the branches.

[jgabry]

This looks good, thanks! After I merge the SVG updates in #460 we can update this branch and run the checks again before merging.

[ishaan-arora-1]

This looks good, thanks! After I merge the SVG updates in #460 we can update this branch and run the checks again before merging.

awesome!!

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.55%. Comparing base (b1cb851) to head (264adcd).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #458   +/-   ##
=======================================
  Coverage   98.55%   98.55%           
=======================================
  Files          35       35           
  Lines        5864     5864           
=======================================
  Hits         5779     5779           
  Misses         85       85           

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