Standardize ActionController::Parameters#to_unsafe_h return value

`ActionController::Parameters#to_h` returns a hash, so lets have
`ActionController::Parameters#to_unsafe_h` return a hash instead of
an `ActiveSupport::HashWithIndifferentAccess` for consistency.

Author: zoltankiss

actionpack/lib/action_controller/metal/strong_parameters.rb

@@ -183,7 +183,7 @@ def to_h
 
     # Returns an unsafe, unfiltered +Hash+ representation of this parameter.
     def to_unsafe_h
-      @parameters
+      @parameters.to_h
     end
     alias_method :to_unsafe_hash, :to_unsafe_h