Exempt np.linalg.solve call from nopython mode

[timothy-nunn]

Thanks @nickodell for this great suggestion. This stops numba from compiling the linalg.solve against SciPy's solvers and uses numpy's linear algebra in normal (non-Numba) mode. I also took this opportunity to remove the asfortranarray because that is not necessary (and possibly has never been)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 43.06%. Comparing base (aff2888) to head (62487ff).
⚠️ Report is 199 commits behind head on main.

Files with missing lines	Patch %	Lines
process/tf_coil.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3856      +/-   ##
==========================================
- Coverage   46.67%   43.06%   -3.62%     
==========================================
  Files         122      123       +1     
  Lines       27806    33237    +5431     
==========================================
+ Hits        12978    14312    +1334     
- Misses      14828    18925    +4097     

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[jonmaddock]

Brilliant, but needs a comment about why this is required.