Follow up from !103652 to use `deprecate_vulnerabilities_feedback` FF

Implementation plan:

!103652 (comment 1182831767) This one I do not think we need this, we can introduce FF when we are using these methods (dismissal_feedback, issue_feedback, merge_request_feedback). This will be covered here !106992 (merged).
!103652 (comment 1182831776)
!103652 (comment 1182831783)

Edited Jan 05, 2023 by Subashis Chakraborty