compiler: Simplify fission

[FabioLuporini]

without this simplification (which was done in 2021, now it seems unneeded, AFAICT based on the tests I've managed to run...) a new test in PRO would fail

I don't see the logic behind it, so unless CI/CD complains, I'd drop it

It might also be a leftover from some other tweaks that was later undone... not sure!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.54%. Comparing base (85e7304) to head (766d39e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2973      +/-   ##
==========================================
+ Coverage   83.53%   83.54%   +0.01%     
==========================================
  Files         257      257              
  Lines       53576    53576              
  Branches     4585     4585              
==========================================
+ Hits        44753    44759       +6     
+ Misses       8029     8025       -4     
+ Partials      794      792       -2     

Flag	Coverage Δ
pytest-gpu-aomp-amdgpuX	68.38% <73.68%> (+<0.01%)	⬆️
pytest-gpu-gcc-	78.38% <100.00%> (+<0.01%)	⬆️
pytest-gpu-icx-	78.33% <100.00%> (+0.02%)	⬆️
pytest-gpu-nvc-nvidiaX	69.04% <73.68%> (-0.02%)	⬇️

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