docs: Sink Historical event data to ClickHouse instructions for non-default settings

Added instructions on how to sink historical event data to ClickHouse if not using default tutor installation

Author: sagar-manprax

README.rst

@@ -66,6 +66,8 @@ Usage
 #. (Optional) Sink Historical event data to ClickHouse::
 
     tutor [dev|local] run lms ./manage.py lms transform_tracking_logs --source_provider LOCAL --source_config '{"key": "/openedx/data", "container": "logs", "prefix": "tracking.log"}' --transformer_type xapi
+    # Note that this will work only for default tutor installation. If you store your tracking logs any other way, you need to change the source_config option accordingly.
+    # See https://event-routing-backends.readthedocs.io/en/latest/howto/how_to_bulk_transform.html#sources-and-destinations for details on how to change the source_config option.
 
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