Fix invalid numpy dtype

[ricardoV94]

There were some bugs that survived along time, until numpy 2.3.0 where it finally fails.

first showed up in #1182

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📚 Documentation preview 📚: https://pytensor--1456.org.readthedocs.build/en/1456/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.12%. Comparing base (0ea61bc) to head (0efe70b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1456   +/-   ##
=======================================
  Coverage   82.12%   82.12%           
=======================================
  Files         211      211           
  Lines       49757    49757           
  Branches     8819     8819           
=======================================
  Hits        40862    40862           
  Misses       6715     6715           
  Partials     2180     2180           

Files with missing lines	Coverage Δ
pytensor/gradient.py	78.55% <100.00%> (ø)
pytensor/scalar/basic.py	80.56% <100.00%> (ø)
pytensor/sparse/rewriting.py	76.15% <100.00%> (ø)

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