docs, hide inflector comment targeting only contributors. [ci skip]

This is a follow up to: 07c7024

As suggested by @fxn this comment should not be visible in the API:
07c7024#commitcomment-5331658

activesupport/lib/active_support/inflections.rb

@@ -1,9 +1,11 @@
 require 'active_support/inflector/inflections'
 
-# Define the standard inflection rules. These define a starting point for
+#--
+# Defines the standard inflection rules. These are the starting point for
 # new projects and are not considered complete. The current set of inflection
 # rules is frozen. This means, we do not change them to become more complete.
 # This is a safety measure to keep existing applications from breaking.
+#++
 module ActiveSupport
   Inflector.inflections(:en) do |inflect|
     inflect.plural(/$/, 's')