Added note for retry related configuration. (GoogleCloudDataproc#1320)

Author: ShreyasSinha

gcs/CONFIGURATION.md

@@ -390,6 +390,8 @@ Knobs configure the vectoredRead API
 
     Proxy password that connector can use to send Cloud Storage requests.
 
+**Note: Retry configuration is only valid for HTTP_API_CLIENT client type for now.**
+
 *   `fs.gs.http.max.retry` (default: `10`)
 
     The maximum number of retries for low-level HTTP requests to Google Cloud