Hide action buttons in loading table rows

What does this MR do?

This prevents action buttons from showing in the skeleton rows while the security dashboard is loading.

This is what we currently see:

This is what we'll see after the fix:

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Style guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.