Add database debug hint in development doc

Add a link on how to use `Verbose Query Logs` in rails console to trace
the source of SQL query. It is useful hint for debugging and identifying
performance problems.

doc/development/README.md

@@ -107,6 +107,7 @@ description: 'Learn how to contribute to GitLab.'
 ### Debugging
 
 - Tracing the source of an SQL query using query comments with [Marginalia](database_query_comments.md)
+- Tracing the source of an SQL query in Rails console using [Verbose Query Logs](https://guides.rubyonrails.org/debugging_rails_applications.html#verbose-query-logs)
 
 ### Best practices