Clear approval state caching after update

This is to recompute the new overall_approvers
In this method, the following calls would cause a change in the
database which needs resetting the cache:

- super (which updates MR)
- sync_approval_rules (which updates rule record's approvals_required)
- cleanup_approvers (which removes any approver not mentioned in params)

resetting cache must be done after those three calls,
so moving some calls earlier is required.
However this would not affect outcome.

ee/app/services/ee/merge_requests/update_service.rb

@@ -13,6 +13,13 @@ def execute(merge_request)
         old_approvers = merge_request.overall_approvers(exclude_code_owners: true)
 
         merge_request = super(merge_request)
+        sync_approval_rules(merge_request)
+
+        if should_remove_old_approvers && merge_request.valid?
+          cleanup_approvers(merge_request, reload: true)
+        end
+
+        merge_request.reset_approval_cache!
 
         new_approvers = merge_request.overall_approvers(exclude_code_owners: true) - old_approvers
 
@@ -21,12 +28,6 @@ def execute(merge_request)
           notification_service.add_merge_request_approvers(merge_request, new_approvers, current_user)
         end
 
-        if should_remove_old_approvers && merge_request.valid?
-          cleanup_approvers(merge_request, reload: true)
-        end
-
-        sync_approval_rules(merge_request)
-
         merge_request
       end