Fixes #4764 - remove generated new line in routes.rb on scaffold generation

As explained in #4764, when destroying a scaffold, routes.rb loses a
new line. This seems to happen because a new line is added
while generating the route and the destroy generator removes it.
However, this causes a problem if the routes file is manually edited
to remove such new lines. This commit just removes that extra new line
from added in the first place.

railties/lib/rails/generators/actions.rb

@@ -246,7 +246,7 @@ def route(routing_code)
         sentinel = /\.routes\.draw do\s*$/
 
         in_root do
-          inject_into_file 'config/routes.rb', "\n  #{routing_code}\n", { :after => sentinel, :verbose => false }
+          inject_into_file 'config/routes.rb', "\n  #{routing_code}", { :after => sentinel, :verbose => false }
         end
       end