Move resolve clauses to the main routes file

We're going to add some constraints in the routes file, and if we add a
`resolve` clause inside a constraints block, we get an error saying that
"The resolve method can't be used inside a routes scope block" when
starting the application.

config/routes/community.rb

@@ -1,5 +1,3 @@
 resources :communities, only: [:show] do
   resources :topics
 end
-
-resolve("Topic") { |topic, options| [topic.community, topic, options] }