Cleanup various controllers (#10972)

* Remove skip_session! as it is not supported in Rails 5

* Minor cleanup in StreamEntriesController

* Remove redundant mark_cacheable! calls

app/controllers/application_controller.rb

@@ -152,11 +152,6 @@ class ApplicationController < ActionController::Base
   end
 
   def mark_cacheable!
-    skip_session!
     expires_in 0, public: true
   end
-
-  def skip_session!
-    request.session_options[:skip] = true
-  end
 end