Remove duplicate code (rhs_parabolic!) for 2D, 3D

[DanielDoehring]

This removes some unnecessary duplicate code.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1946f9d) 96.34% compared to head (fd3effd) 92.65%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1810      +/-   ##
==========================================
- Coverage   96.34%   92.65%   -3.69%     
==========================================
  Files         450      450              
  Lines       35938    35865      -73     
==========================================
- Hits        34622    33230    -1392     
- Misses       1316     2635    +1319     

Flag	Coverage Δ
unittests	92.65% <100.00%> (-3.69%)	⬇️

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[jlchan]

Looks great - thanks for cleaning this up and making the code simpler. My only suggestion is to add a comment.

[jlchan]

Thanks!