Fix importing PetabImporter without jax and sciml extras

[dweindl]

Closes #3140.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.72%. Comparing base (4e223a0) to head (cd6c8b3).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3141      +/-   ##
==========================================
- Coverage   77.35%   76.72%   -0.64%     
==========================================
  Files         318      317       -1     
  Lines       20631    20628       -3     
  Branches     1483     1483              
==========================================
- Hits        15959    15826     -133     
- Misses       4664     4794     +130     
  Partials        8        8              

Flag	Coverage Δ
cpp	70.44% <ø> (+<0.01%)	⬆️
cpp_python	37.14% <ø> (-0.67%)	⬇️
petab	47.16% <ø> (+<0.01%)	⬆️
python	68.90% <ø> (+<0.01%)	⬆️
sbmlsuite-jax	?

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Files with missing lines	Coverage Δ
...hon/sdist/amici/importers/petab/_petab_importer.py	86.74% <ø> (ø)
python/sdist/amici/sim/jax/petab.py	68.04% <ø> (ø)

... and 4 files with indirect coverage changes

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