Update indexer config in doc

developer-docs-site/docs/indexer/legacy/migration.md

@@ -32,12 +32,15 @@ For each processor you're migrating, you'll need to create a config file using t
 ```yaml
 health_check_port: 8084
 server_config:
-  processor_name: default_processor
+  processor_config:
+    type: default_processor
   postgres_connection_string: <postgres_uri, e.g. postgresql://postgres:@localhost:5432/indexer>
   indexer_grpc_data_service_address: <url_from_api_gateway>
   indexer_grpc_http2_ping_interval_in_secs: 60
   indexer_grpc_http2_ping_timeout_in_secs: 10
   auth_token: <auto_token_from_api_gateway>
+  starting_version: 0 # optional
+  ending_version: 0 # optional
 ```
 
 To connect the processor to the Transaction Stream Service, you need to set the URL for `indexer_grpc_data_service_address`. Choose one of the following options.