Resolve "Fixed vulnerabilities should not be actionable in the report"

What does this MR do?

Moves the shouldRenderFooterSection() computed prop into methods so we can bust the cache.

Why was this MR needed?

Because Vue was caching the result of the function on page load and never re-computing it. It's a known issue quirk of Vue and is similar (but not quite the same as) the issue outlined here.

Moving the whole thing to a method means we lose the speed gains of vue's computed caching for this function. But since it's a boolean check that only runs twice when you open a new modal, the caching is a luxury we can afford to lose.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conform by the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• EE specific content should be in the top level /ee folder
• Conform by the merge request performance guides
• Conform by the style guides
• Conform by the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

Closes #6017 (closed)