Do not reference Gitter

Author: fthomas

README.md

@@ -218,8 +218,7 @@ Consider creating PR to add your company to the list and join the community.
 ## Participation
 
 The Scala Steward project supports the [Scala Code of Conduct][CoC]
-and wants all of its channels (GitHub, Gitter, etc.) to be welcoming
-environments for everyone.
+and wants all of its channels to be welcoming environments for everyone.
 
 ## Credit