update RPS

Author: Ling-Cao

articles/ai-services/speech-service/batch-synthesis-properties.md

@@ -115,7 +115,7 @@ The specified entity can't be found. Make sure the synthesis ID is correct.
 
 ### HTTP 429 error
 
-There are too many recent requests. Each client application can submit up to 50 requests per 5 seconds for each Speech resource. Reduce the number of requests per second.
+There are too many recent requests. Each client application can submit up to 100 requests per 10 seconds for each Speech resource. Reduce the number of requests per second.
 
 ### HTTP 500 error