feat: remove additional notes section and related placeholders from default.md

Author: tanhongit

.gitlab/merge_request_templates/default.md

@@ -23,8 +23,3 @@
 * [ ] Code matches the confirmed solution in the ticket.
 * [ ] Unit/Integration tests have been added or updated.
 * [ ] Env/Config/DB changes were confirmed by @cslant/admin.
-
-## Additional Notes
-
-/assign me
-/draft