Version bump to v2.4.0.beta6

Version bump to v2.4.0.beta6

diff --git a/lib/version.rb b/lib/version.rb
index 45d3950..2116856 100644
--- a/lib/version.rb
+++ b/lib/version.rb
@@ -9,7 +9,7 @@ module Discourse
       MAJOR = 2
       MINOR = 4
       TINY  = 0
-      PRE   = 'beta5'
+      PRE   = 'beta6'
 
       STRING = [MAJOR, MINOR, TINY, PRE].compact.join('.')
     end

GitHub sha: 09021c35