Changed docs to make it clear which CODEOWNERS file is taken into account in MRs

doc/user/project/code_owners.md

@@ -48,10 +48,14 @@ You can choose to add the `CODEOWNERS` file in three places:
 - Inside the `.gitlab/` directory
 - Inside the `docs/` directory
 
-The `CODEOWNERS` file is scoped to a branch, which means that as
-new files are introduced, the user adding the new content can
-specify themselves as a code owner, all before the new changes
-get merged to the target branch.
+The `CODEOWNERS` file is valid for the branch where it lives. For example, if you change the code owners
+in a feature branch, they won't be valid in the main branch until the feature branch is merged.
+
+If you introduce new files to your repository and you want to identify the code owners for that file,
+you have to update `CODEOWNERS` accordingly. If you update the code owners when you are adding the files (in the same
+branch), GitLab will count the owners as soon as the branch is merged. If
+you don't, you can do that later, but your new files will not belong to anyone until you update your
+`CODEOWNERS` file in the TARGET branch.
 
 When a file matches multiple entries in the `CODEOWNERS` file,
 the users from last pattern matching the file are displayed on the