Fix some simple type checking in gui

[eivindjahren]

Adds some simple missing typehints to gui

• [x] PR title captures the intent of the changes, and is fitting for release notes.
• [x] Added appropriate release note label
• [x] Commit history is consistent and clean, in line with the contribution guidelines.
• [x] 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 98.75000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 86.07%. Comparing base (99a29f6) to head (bbd250f). Report is 1 commits behind head on main.

Files	Patch %	Lines
src/ert/gui/tools/workflows/run_workflow_widget.py	70.00%	3 Missing :warning:
src/ert/gui/ertwidgets/statusdialog.py	87.50%	1 Missing :warning:
src/ert/gui/main.py	66.66%	1 Missing :warning:
src/ert/gui/plottery/plots/observations.py	66.66%	1 Missing :warning:
src/ert/gui/tools/plot/filterable_kw_list_model.py	75.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #8083 +/- ## ========================================== + Coverage 86.02% 86.07% +0.04% ========================================== Files 382 382 Lines 23621 23679 +58 Branches 620 619 -1 ========================================== + Hits 20321 20381 +60 + Misses 3222 3219 -3 - Partials 78 79 +1 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.