Update dbt.md to add user role

mention about required permissions

Author: muhammadatifjav

src/segment-app/extensions/dbt.md

@@ -28,6 +28,7 @@ To set up the dbt extension, you'll need:
 
 - an existing dbt account with a Git repository
 - for job syncs, dbt cloud with jobs already created
+- a user with "Workspace Owner" permissions in Segment
 
 ### Git repository and dbt Models setup