Mention branch protection ordering (#11217)

Author: trask

.github/repository-settings.md

@@ -20,6 +20,11 @@ settings](https://github.com/open-telemetry/community/blob/main/docs/how-to-conf
 
 ## Branch protections
 
+The order of branch protection rules
+[can be important](https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/managing-a-branch-protection-rule#about-branch-protection-rules).
+The branch protection rules below should be added before the `**/**` branch protection rule
+(this may require deleting the `**/**` rule and recreating it at the end).
+
 ### `main`
 
 - Require branches to be up to date before merging: UNCHECKED