docs(datahub-kafka-sink): add topic_routes config to doc

metadata-ingestion/sink_docs/datahub.md

@@ -108,6 +108,8 @@ Note that a `.` is used to denote nested fields in the YAML recipe.
 | `connection.producer_config.<option>`        |          |         | Passed to https://docs.confluent.io/platform/current/clients/confluent-kafka-python/html/index.html#confluent_kafka.SerializingProducer                  |
 | `connection.schema_registry_url`             | ✅       |         | URL of schema registry being used.                                                                                                                       |
 | `connection.schema_registry_config.<option>` |          |         | Passed to https://docs.confluent.io/platform/current/clients/confluent-kafka-python/html/index.html#confluent_kafka.schema_registry.SchemaRegistryClient |
+| `topic_routes.MetadataChangeEvent`           |          | MetadataChangeEvent     | Overriden Kafka topic name for the MetadataChangeEvent |
+| `topic_routes.MetadataChangeProposal`        |          | MetadataChangeProposal  | Overriden Kafka topic name for the MetadataChangeProposal |
 
 The options in the producer config and schema registry config are passed to the Kafka SerializingProducer and SchemaRegistryClient respectively.