Ignore inner unused RNG inputs in collect_default_updates

[ricardoV94]

It closes the PyMC-side of #7657.

The example there will still not work due to the OpFromGraph L_op actually re-introducing the random variable (but not the next rng update). That's a PyTensor question, that may be addressed by pymc-devs/pytensor#1174

These changes still make sense on their own.

Closes #7657

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📚 Documentation preview 📚: https://pymc--7658.org.readthedocs.build/en/7658/

[codecov]

Codecov Report

Attention: Patch coverage is 95.23810% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.70%. Comparing base (fa43eba) to head (8d26d62).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
pymc/pytensorf.py	95.23%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7658      +/-   ##
==========================================
- Coverage   92.78%   92.70%   -0.09%     
==========================================
  Files         107      107              
  Lines       18196    18391     +195     
==========================================
+ Hits        16884    17050     +166     
- Misses       1312     1341      +29     

Files with missing lines	Coverage Δ
pymc/pytensorf.py	90.67% <95.23%> (+<0.01%)	⬆️

... and 7 files with indirect coverage changes

[jessegrabowski]

Small typo, otherwise looks great