Update docs_pull_request_template.md

Author: egil

.github/PULL_REQUEST_TEMPLATE/docs_pull_request_template.md

@@ -11,6 +11,6 @@ assignees:
 -->
 
 ### PR meta checklist
-- [ ] Pull request is targeting the `main` branch.
+- [ ] Pull request is targeting the `MAIN` branch.
 - [ ] Pull request is linked to all related issues, if any.
 - [ ] I have read relevant parts of the _CONTRIBUTING.md_ document and _docs/README.md_.