docs(): Update readme (#1176)

Author: davideast

README.md

@@ -26,12 +26,8 @@ Status: Release candidate
 
 ```bash
 npm install firebase angularfire2 --save
-# Or use the 5.0 beta API! Will be released soon
-npm install firebase angularfire2@next --save
 ```
 
-## Note: These docs reference the beta 5.0 API which will be released soon.
-
 ## Example use:
 
 ```ts