Update client docs version string to 2.4.0

Need to update this to match the latest version.

doc/conf.py

@@ -48,9 +48,9 @@ copyright = u'2013-2016, The ownCloud developers'
 # built documents.
 #
 # The short X.Y version.
-version = '2.3.0'
+version = '2.4.0'
 # The full version, including alpha/beta/rc tags.
-release = '2.3.0'
+release = '2.4.0'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.