Update play-action.md

increased character limit from 400 to 4000 and listed no support for HD voices

Author: valindrae

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

@@ -48,7 +48,8 @@ This guide will help you get started with playing audio files to participants by
 |PlayFailed | 500 | 8572 | Action failed due to play service shutdown. |
 
 ## Known limitations
-- 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.
+- HD Voices from Azure AI Foundry are not officially supported, these will result in timeuouts if used. 
 - For scenarios where you exceed your Speech service quota limit, you can request to increase this limit by following the steps outlined [here](/azure/ai-services/speech-service/speech-services-quotas-and-limits).
 
 ## Clean up resources