[24.2] Fix simple activity panel item style

[guerler]

This PR adjusts for recent changes to the activity panel. Unnecessary styles are removed from the activity settings panel and now missing styles are restored for the visualizations panel.

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. Navigate to the Visualizations Panel
  2. Without this PR: Notice that the options are misaligned
  3. With this PR: Verify that the Settings Activity Panel and the Visualizations Panel item look and behave the same

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.