Add link for violated commits

What does this MR do and why?

This MR adds a link to the unsigned commits listed in the detailed policy bot comment.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

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Before	After

How to set up and validate locally

1. In rails console enable the feature flag

   Feature.enable(:save_policy_violation_data)

2. Create a new project
3. Go to Secure -> Policies and create a new policy:

   type: approval_policy
   name: Any MR
   description: ''
   enabled: true
   rules:
     - type: any_merge_request
       branch_type: protected
       commits: unsigned
   actions:
     - type: require_approval
       approvals_required: 1
       role_approvers:
         - developer
   approval_settings:
     block_branch_modification: false
     prevent_pushing_and_force_pushing: false
     prevent_approval_by_author: true
     prevent_approval_by_commit_author: true
     remove_approvals_with_new_commit: true
     require_password_to_approve: true

4. In the project, create an MR that updates README using Web IDE
5. Verify that approvals for Any MR are required and the commit listed in the comment is a functioning link

Related to #433403 (closed)