[ci skip] Add warning note to :source_location tag option (rails#55167)

* Add warning note to :source_location tag option

`:source_location` adds significant overhead to each SQL query issued from Rails application. Whilst this behaviour has been noted in changelog, it is not noticeable when reading the official documentation on Rails application configuration.

Co-authored-by: Hartley McGuire <[email protected]>

Author: dizlv

guides/source/configuring.md

@@ -1488,6 +1488,8 @@ Define an `Array` specifying the key/value tags to be inserted in an SQL comment
 `[ :application, :controller, :action, :job ]`. The available tags are: `:application`, `:controller`,
 `:namespaced_controller`, `:action`, `:job`, and `:source_location`.
 
+WARNING: Calculating the `:source_location` of a query can be slow, so you should consider its impact if using it in a production environment.
+
 #### `config.active_record.query_log_tags_format`
 
 A `Symbol` specifying the formatter to use for tags. Valid values are `:sqlcommenter` and `:legacy`.