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/following_accounts_controller.rb

@@ -19,10 +19,7 @@ class FollowingAccountsController < ApplicationController
       format.json do
         raise Mastodon::NotPermittedError if params[:page].present? && @account.user_hides_network?
 
-        if params[:page].blank?
-          skip_session!
-          expires_in 3.minutes, public: true
-        end
+        expires_in 3.minutes, public: true if params[:page].blank?
 
         render json: collection_presenter,
                serializer: ActivityPub::CollectionSerializer,