chore: update pr template (#5113)

Add an information to enable `Allow edits from maintainers`. Seems to be disabled by default.

.github/pull_request_template.md

 <!--
     Before submitting a Pull Request, please ensure you have signed the CLA using this GitHub App:
     https://cla-assistant.io/renovateapp/renovate
+
+    Please ensure `Allow edits from maintainers.` checkbox is checked
 -->
 
 <!-- Replace this text with a description of what this PR fixes or adds -->