Remove unnecessary fixtures

[dafeda]

Pre review checklist

• Added appropriate release note label
• PR title captures the intent of the changes, and is fitting for release notes.
• Commit history is consistent and clean, in line with the contribution guidelines.

Adding labels helps the maintainers when writing release notes. This is the list of release note labels.

[codecov-commenter]

Codecov Report

Merging #3735 (7f1a3a5) into main (f9042c7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #3735   +/-   ##
=======================================
  Coverage   62.73%   62.73%           
=======================================
  Files         592      592           
  Lines       45844    45844           
  Branches     4127     4127           
=======================================
  Hits        28762    28762           
+ Misses      15818    15817    -1     
- Partials     1264     1265    +1     

Impacted Files	Coverage Δ
src/libres/lib/res_util/block_fs.cpp	67.34% <0.00%> (-0.41%)	⬇️
src/ert/data/record/_transformation.py	89.04% <0.00%> (+0.47%)	⬆️

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[sondreso]

LGTM!