auto_html version requirements holding back rexml upgrade

[KieranP]

https://www.ruby-lang.org/en/news/2024/07/16/dos-rexml-cve-2024-39908/

auto_html (2.1.1) requires rexml (~> 3.2.5)

Which means I cannot upgrade to rexml 3.3.2 or later which includes the bug fixes.