Use wait_for_child for getting RunDialog in test

[eivindjahren]

Quick cleanup of comment and fetching of RunDialog in test_restart_ensemble

• [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 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 :white_check_mark:

Project coverage is 91.38%. Comparing base (e607feb) to head (bb7f4be). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #8823 +/- ## ========================================== + Coverage 91.31% 91.38% +0.06% ========================================== Files 342 342 Lines 21028 21028 ========================================== + Hits 19202 19216 +14 + Misses 1826 1812 -14 ``` | [Flag](https://app.codecov.io/gh/equinor/ert/pull/8823/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | Coverage Δ | | |---|---|---| | [cli-tests](https://app.codecov.io/gh/equinor/ert/pull/8823/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | `39.62% <ø> (-0.02%)` | :arrow_down: | | [gui-tests](https://app.codecov.io/gh/equinor/ert/pull/8823/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | `73.58% <ø> (+0.12%)` | :arrow_up: | | [performance-tests](https://app.codecov.io/gh/equinor/ert/pull/8823/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | `50.05% <ø> (ø)` | | | [unit-tests](https://app.codecov.io/gh/equinor/ert/pull/8823/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | `79.82% <ø> (-0.02%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor#carryforward-flags-in-the-pull-request-comment) to find out more.

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