Upgrade ReXML to version 3.4.4
Closes #1.
New version released on 10'th of September 2025
: https://github.com/ruby/rexml/releases/tag/v3.4.4
Vulnerability disclosure for older version: https://www.ruby-lang.org/en/news/2025/09/18/dos-rexml-cve-2025-58767/
Version diff: https://github.com/ruby/rexml/compare/v3.4.1...v3.4.4