[ruby/io-console] [DOC] Note that IO#getpass returns a chomped string

IO#getpass uses String#chomp! on the read input line.

https://github.com/ruby/io-console/commit/1e98c93bc8

ext/io/console/console.c

@@ -1574,6 +1574,10 @@ str_chomp(VALUE str)
  * Reads and returns a line without echo back.
  * Prints +prompt+ unless it is +nil+.
  *
+ * The newline character that terminates the
+ * read line is removed from the returned string,
+ * see String#chomp!.
+ *
  * You must require 'io/console' to use this method.
  */
 static VALUE