fix(HeadlineEditor): Add css class for any level option

[tvdeyen]

What is this pull request for?

We changed that we always show the level select on the headline editor in bd056bd7c but have not adjusted that the css class (with-level-select) is always added.

Screenshots

Checklist

• [x] I have followed Pull Request guidelines
• [x] I have added a detailed description into each commit message
• [x] I have added tests to cover this change

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.96%. Comparing base (a3d5bee) to head (033b3d5). Report is 3 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2905 +/- ## ======================================= Coverage 95.96% 95.96% ======================================= Files 232 232 Lines 6273 6273 ======================================= Hits 6020 6020 Misses 253 253 ```

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