Remove beta feature comments per GA (#211)

Author: rogebrd

dropbox/oauth.py

@@ -40,9 +40,6 @@
 class OAuth2FlowNoRedirectResult(object):
     """
     Authorization information for an OAuth2Flow performed with no redirect.
-
-    Currently refresh_token and expiration are both beta features, if you are interested
-    in using them, please contact Dropbox support
     """
 
     def __init__(self, access_token, account_id, user_id, refresh_token, expiration, scope):

example/oauth/commandline-oauth-pkce.py

@@ -4,10 +4,6 @@
 from dropbox import DropboxOAuth2FlowNoRedirect
 
 '''
-This example uses PKCE, a currently beta feature.
-If you are interested in using this, please contact
-Dropbox support
-
 Populate your app key in order to run this locally
 '''
 APP_KEY = ""

example/oauth/commandline-oauth-scopes.py

@@ -4,10 +4,6 @@
 from dropbox import DropboxOAuth2FlowNoRedirect
 
 '''
-This example uses Scopes, a currently beta feature.
-If you are interested in using this, please contact
-Dropbox support
-
 It goes through an example of requesting a starting scope,
 and requesting more throughout the process
 '''