Fix pytest option typo

[HakonSohoel]

Issue
Resolves #9140

Approach
Short description of the approach

(Screenshot of new behavior in GUI if applicable)

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'pytest tests/ert/unit_tests -n logical -m "not integration_test"')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.75%. Comparing base (8c679c1) to head (136fcea).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9141      +/-   ##
==========================================
- Coverage   90.78%   90.75%   -0.03%     
==========================================
  Files         351      351              
  Lines       21889    21889              
==========================================
- Hits        19871    19865       -6     
- Misses       2018     2024       +6     

Flag	Coverage Δ
cli-tests	39.23% <ø> (+<0.01%)	⬆️
gui-tests	71.79% <ø> (ø)
performance-tests	49.41% <ø> (+<0.01%)	⬆️
unit-tests	79.65% <ø> (-0.04%)	⬇️

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[eivindjahren]

👍