Harmonize HSGP.prior dimension names and order

[juanitorduz]

Closes #7561

and changes the order of the dims, see #7561 (comment)

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📚 Documentation preview 📚: https://pymc--7562.org.readthedocs.build/en/7562/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.83%. Comparing base (3057351) to head (af142c4).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7562   +/-   ##
=======================================
  Coverage   92.83%   92.83%           
=======================================
  Files         106      106           
  Lines       17669    17669           
=======================================
  Hits        16403    16403           
  Misses       1266     1266           

Files with missing lines	Coverage Δ
pymc/gp/hsgp_approx.py	88.39% <100.00%> (ø)

[bwengals]

Good catch!