Update code_review.md to include a recommendation for assigning maintainers from different teams

Improve recommended maintainer docs

doc/development/code_review.md

@@ -27,8 +27,9 @@ There are a few rules to get your merge request accepted:
    ask or assign any [reviewers][projects] for a first review.
    1. If you need some guidance (e.g. it's your first merge request), feel free
       to ask one of the [Merge request coaches][team].
-   1. The reviewer will assign the merge request to a maintainer once the
-      reviewer is satisfied with the state of the merge request.
+   1. It is recommended that you assign a maintainer that is from a different team than your own.
+      This ensures that all code across GitLab is consistent and can be easily understood by all contributors.
+      
 1. Keep in mind that maintainers are also going to perform a final code review.
    The ideal scenario is that the reviewer has already addressed any concerns
    the maintainer would have found, and the maintainer only has to perform the