Relax requirement for flaky cpu multiprocess test

[berland]

Issue
Resolves 🩸 with 🩹 (#8798 )

Approach
🕐

• 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 90.93%. Comparing base (64bbc7e) to head (c0bbc88).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #9040   +/-   ##
=======================================
  Coverage   90.92%   90.93%           
=======================================
  Files         352      352           
  Lines       21712    21712           
=======================================
+ Hits        19742    19743    +1     
+ Misses       1970     1969    -1     

Flag	Coverage Δ
cli-tests	39.12% <ø> (+0.17%)	⬆️
gui-tests	72.66% <ø> (ø)
performance-tests	49.56% <ø> (+0.01%)	⬆️
unit-tests	79.65% <ø> (-0.01%)	⬇️

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[eivindjahren]

👍