mark the reporter as public api

Author: JonRowe

lib/rspec/core/configuration.rb

@@ -825,7 +825,7 @@ def play_onto(reporter)
         end
       end
 
-      # @private
+      # @return [RSpec::Core::Reporter] the currently configured reporter
       def reporter
         # @reporter_buffer should only ever be set in this method to cover
         # initialization of @reporter.