marking self in Hash#symbolize_keys!

activesupport/lib/active_support/core_ext/hash/keys.rb

@@ -35,7 +35,7 @@ def symbolize_keys
   alias_method :to_options,  :symbolize_keys
 
   # Destructively convert all keys to symbols, as long as they respond
-  # to +to_sym+. Same as +symbolize_keys+, but modifies self.
+  # to +to_sym+. Same as +symbolize_keys+, but modifies +self+.
   def symbolize_keys!
     keys.each do |key|
       self[(key.to_sym rescue key)] = delete(key)