Update README.md (signalfx#64)

Author: theletterf

README.md

@@ -1,6 +1,6 @@
 # Splunk Distribution of OpenTelemetry for React Native
 
-> :construction: This project is currently **Experimental**. Do not use it in production environments.
+> :construction: This distribution is currently in beta. Don’t use it in production environments without extensive prior testing. Some features might not be supported or might have constrained capabilities.
 
 ## Overview