Remove caveat from doc (fsspec#666)

Author: martindurant

docs/source/index.rst

@@ -3,8 +3,6 @@ GCSFS
 
 A pythonic file-system interface to `Google Cloud Storage`_.
 
-This software is beta, use at your own risk.
-
 Please file issues and requests on github_ and we welcome pull requests.
 
 .. _github: https://github.com/fsspec/gcsfs/issues