Lobby message: update with 2.7 expected release date & 2.7 megathread…

… URL (#12782)

servers.yml

@@ -8,11 +8,13 @@ servers:
   - version: "2.5.22294"
     lobby_uri: https://prod.triplea-game.org
     message: |
+      Release 2.7 is expected in late October. For early access,
+      latest info, or to help volunteer with release testing, see:
+          https://tinyurl.com/release-27
+
       Welcome to the TripleA lobby!
       Please no politics, stay respectful, be welcoming, have fun.
 
-      2.6 Update: The 2.6 release is back into a testing phase!
-      Follow 2.6 status on forums: https://tinyurl.com/triplea26
   - version: "2.0.20057"
     inactive: true
   - version: "0.0"