Remove misplaced comment [ci-skip]

This comment was accidentally left in 1b9e85d.

(cherry picked from commit a9a12a1)

Author: jonathanhefner

actionview/lib/action_view/test_case.rb

@@ -301,7 +301,6 @@ def _routes
       class RenderedViewContent < String # :nodoc:
       end
 
-      # Need to experiment if this priority is the best one: rendered => output_buffer
       class RenderedViewsCollection
         def initialize
           @rendered_views ||= Hash.new { |hash, key| hash[key] = [] }