Change variable name in Ruby alias_method_chain

`method_name` is more clear than `name`, and follows the style of the
other snippets.

snippets/ruby.snippets

@@ -210,7 +210,7 @@ snippet defds
 snippet am
 	alias_method :${1:new_name}, :${0:old_name}
 snippet amc
-	alias_method_chain :${1:name}, :${0:feature}
+	alias_method_chain :${1:method_name}, :${0:feature}
 snippet app
 	if __FILE__ == $PROGRAM_NAME
 		${0}