Added TargetBranchRules::DestroyService service

What does this MR do and why?

Creates the service that will destroy existing target branch rules.

DELETE FROM target_branch_rules
WHERE
    target_branch_rules.id = 3;

Screenshots or screen recordings

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

#17909 (closed)