Update call-automation-sdk.md

Added 503 error code

Author: alvin-l-han

articles/communication-services/resources/troubleshooting/voice-video-calling/includes/codes/call-automation-sdk.md

@@ -28,4 +28,5 @@ The following error codes are exposed by the Call Automation SDK.
 | | 500 | Internal server error | | Retry after a delay. If it persists, raise a support ticket. |
 | | 500 | Play Failed | | File a support request through the Azure portal. |
 | | 500 | Recognize Failed | | Check error message and confirm the audio file format is valid (WAV, 16 KHz, Mono). If the file format is valid, file a support request through Azure portal. |
-| | 502 | Bad gateway | | Retry after a delay with a fresh http client. |
+| | 502 | Bad gateway | | Retry after a delay with a fresh http client. |
+| | 503 | Communication Services infrastructure error. | | File a support request through the Azure portal. |