Fix filter popup not closing

[frode-aarstad]

Issue
Resolves #8380

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 tests pass locally (after every commit!)

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

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.87%. Comparing base (50a9869) to head (a03c86d).
Report is 11 commits behind head on main.

Files	Patch %	Lines
src/ert/gui/tools/plot/filter_popup.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8390      +/-   ##
==========================================
- Coverage   90.88%   90.87%   -0.01%     
==========================================
  Files         347      347              
  Lines       21076    21068       -8     
==========================================
- Hits        19154    19145       -9     
- Misses       1922     1923       +1     

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[dafeda]

It can still hang if we leave the filter window immediately after clicking the filter-button but I guess this is Qt thing.