Fix mr approvals code after notification_service refactoring

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/services/notification_service.rb

@@ -379,7 +379,7 @@ class NotificationService
   end
 
   def approve_mr_email(merge_request, project, current_user)
-    recipients = build_recipients(merge_request, project, current_user)
+    recipients = NotificationRecipientService.new(project).build_recipients(merge_request, current_user)
 
     recipients.each do |recipient|
       mailer.approved_merge_request_email(recipient.id, merge_request.id, current_user.id).deliver_later
@@ -387,7 +387,7 @@ class NotificationService
   end
 
   def unapprove_mr_email(merge_request, project, current_user)
-    recipients = build_recipients(merge_request, project, current_user)
+    recipients = NotificationRecipientService.new(project).build_recipients(merge_request, current_user)
 
     recipients.each do |recipient|
       mailer.unapproved_merge_request_email(recipient.id, merge_request.id, current_user.id).deliver_later