[Cleanup/Followup] Remove update/ignore quick actions in library updates listing

Current	Expected

Spec

1. Ignore and update buttons should be removed from the library updates listing view.
2. Each available update should only show a button to review updates on the right side.

Rationale

This ticket is filed under https://github.com/openedx/frontend-app-authoring/issues/2182 because it is a prerequisite to clarifying local override behavior.

1. Ignore/update should require reviewing changes before a user decides whether to ignore/update or take other actions. As we support overrides and higher-level library structural blocks, it's important to ensure users review changes before approving them.
2. In the future, some content syncs will include more nuanced options than only "ignore" and "update" (e.g. choosing whether to keep local overrides). Dropping the shortcuts will allow the default/secondary option to vary per object for some cases.

In Scope

1. Remove separator
2. Remove ignore and update buttons

Out of scope

Any other changes

Related Issues

• #2182
• https://github.com/openedx/frontend-app-authoring/issues/2174

Start at the library updates listing view and compare it with the current and expected screenshots in the issue. Remove the separator and the Ignore and Update actions, leaving only the Review Updates button on the right; confirm that no other changes are included.