Update rexml to 3.4.4 for Ruby 3.4 (CVE-2025-58767) (ruby#14795)

Update rexml to 3.4.4

[Backport #21632]

Author: Bo98

gems/bundled_gems

@@ -10,7 +10,7 @@ minitest            5.25.4  https://github.com/minitest/minitest
 power_assert        2.0.5   https://github.com/ruby/power_assert
 rake                13.2.1  https://github.com/ruby/rake
 test-unit           3.6.7   https://github.com/test-unit/test-unit
-rexml               3.4.0   https://github.com/ruby/rexml
+rexml               3.4.4   https://github.com/ruby/rexml
 rss                 0.3.1   https://github.com/ruby/rss
 net-ftp             0.3.8   https://github.com/ruby/net-ftp
 net-imap            0.5.8   https://github.com/ruby/net-imap