Remove `if:` argument in before_action and alike when `only:` is also used

What does this MR do?

Closes #55564 (closed)

This is first discovered in https://gitlab.com/gitlab-org/gitlab-ce/issues/54739#note_122609857 that if both if: and only: are used in a before_action or after_action or alike, if: is completely ignored.

What are the relevant issue numbers?

55564

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer