Fix failing kwargs in VI

[penelopeysm]

Running VI with extra kwargs would cause errors. This fixes it.

[github-actions]

Turing.jl documentation for PR #2813 is available at:
https://TuringLang.github.io/Turing.jl/previews/PR2813/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.23%. Comparing base (9402c11) to head (afa33e8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2813   +/-   ##
=======================================
  Coverage   85.23%   85.23%           
=======================================
  Files          22       22           
  Lines        1483     1483           
=======================================
  Hits         1264     1264           
  Misses        219      219           

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