Minibatch warning fix

[zaxtax]

Description

This fixes a small oversight in #7742 where it didn't check all ancestors to an observed value if it contains a MinibatchOp

Checklist

• Checked that the pre-commit linting/style checks pass
• Included tests that prove the fix is effective or that the new feature works
• Added necessary documentation (docstrings and/or example notebooks)
• If you are a pro: each commit corresponds to a relevant logical change

Type of change

• New feature / enhancement
• Bug fix
• Documentation
• Maintenance
• Other (please specify):

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📚 Documentation preview 📚: https://pymc--7749.org.readthedocs.build/en/7749/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.82%. Comparing base (4185b7b) to head (e955f44).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7749      +/-   ##
==========================================
- Coverage   92.82%   92.82%   -0.01%     
==========================================
  Files         107      107              
  Lines       18326    18325       -1     
==========================================
- Hits        17011    17010       -1     
  Misses       1315     1315              

Files with missing lines	Coverage Δ
pymc/model/core.py	93.02% <100.00%> (+0.02%)	⬆️

... and 2 files with indirect coverage changes

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