Media Library message persists after deselecting items to fix overflow

Problem/Motivation

When a user selects more media items than allowed by a field's cardinality limit and clicks "Insert selected", an error message is displayed: "There are currently X items selected. The maximum number of items for the field is Y. Remove Z items from the selection."

However, when the user deselects items to get back within the allowed limit, this message remains visible until they click "Insert selected" again. This creates a confusing UX where the user has already corrected the issue but still sees the error.

Steps to reproduce

1. Enable media_library module
2. Add a media field to basic page content type
3. Create a basic page
4. Click on Add Media to the field you created
5. Add a file on "Choose File"
6. Save
7. Add another file on "Choose File"
8. The message should appear
9. Deselect one of the media items previously uploaded
10. Notice the message is still visible

Proposed resolution

Clear the #media-library-messages container in the checkEnabled() JavaScript function in media_library.ui.js when the selection count returns to within the allowed limit.

Remaining tasks

- Review
- Test

User interface changes

Error/warning messages in the media library modal are now automatically cleared when the user deselects items to return within the field's cardinality limit.

Introduced terminology

None

API changes

None

Data model changes

None

Release notes snippet

None