Removed unused variable in proc

 * This unused variable is already removed from the code here. d18e8b1a

 * So removing it from CHANGELOG to be consistent with code

actionpack/CHANGELOG.md

@@ -7,7 +7,7 @@
 
         layout nil
 
-        layout proc { |c| nil }
+        layout proc { nil }
 
         layout :returns_nil