Update recognize-action.md

increased character limit from 400 to 4000

Author: valindrae

articles/communication-services/how-tos/call-automation/recognize-action.md

@@ -57,7 +57,7 @@ This guide helps you get started recognizing DTMF input provided by participants
 
 ## Known limitations
 - In-band DTMF isn't supported. Use RFC 2833 DTMF instead.
-- Text-to-Speech text prompts support a maximum of 400 characters, if your prompt is longer than this we suggest using SSML for Text-to-Speech based play actions.
+- Text-to-Speech text prompts support a maximum of 4000 characters, if your prompt is longer than this we suggest using SSML for Text-to-Speech based play actions.
 - For scenarios where you exceed your Speech service quota limit, you can request to increase this limit by following the steps outlined in [Speech services quotas and limits](/azure/ai-services/speech-service/speech-services-quotas-and-limits).
 
 ## Clean up resources