Merge branch 'update-todos-docs' into 'master'

Update todos docs to say will trigger when commenting on a commit

See merge request gitlab-org/gitlab-ce!18083

doc/workflow/todos.md

@@ -28,11 +28,10 @@ A Todo appears in your Todos dashboard when:
 - an issue or merge request is assigned to you,
 - you are `@mentioned` in an issue or merge request, be it the description of
   the issue/merge request or in a comment,
+- you are `@mentioned` in a comment on a commit,
 - a job in the CI pipeline running for your merge request failed, but this
   job is not allowed to fail.
 
->**Note:** Commenting on a commit will _not_ trigger a Todo.
-
 ### Directly addressed Todos
 
 > [Introduced][ce-7926] in GitLab 9.0.