Remove unnecessary output files in simd_op_check

[stevesuzuki-arm]

Fixes #9130

• Tests added or updated (not required for docs, CI config, or typo fixes)

[stevesuzuki-arm]

Note llvm_assembly is kept as it seems to be deliberately added by @mcourteaux just a couple of months ago.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9131   +/-   ##
=======================================
  Coverage        ?   69.68%           
=======================================
  Files           ?      255           
  Lines           ?    77695           
  Branches        ?    18545           
=======================================
  Hits            ?    54138           
  Misses          ?    18004           
  Partials        ?     5553           

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[mcourteaux]

I was debugging codegen issues I caught by narrowing down the search for the instruction of interest in the op_check. We had just one bug, but inspecting the LLVM assembly was useful at that point. For everyday testing purposes that can also be disabled. Perhaps some sort of verbosity/debugging flag for the simd_op_check is good, if we don't want to just comment this line? @alexreinking