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Fix punctuation

Author: AnnaMHuff

articles/ai-services/speech-service/text-to-speech-avatar/content-credentials.md

@@ -33,7 +33,7 @@ The content credentials are only supported in video files generated by batch syn
 
 ## How do I use content credentials in my solution today?
 
-You can use content credentials by ensuring that your Azure text to speech avatar generated video files contain content credentials
+You can use content credentials by ensuring that your Azure text to speech avatar generated video files contain content credentials.
 
 No extra set-up is necessary. Content credentials are automatically applied to all applicable videos generated by the Azure text to speech avatar.