Update REXML to 3.4.2 or later to fix DOS vulnerability #1026
Description
The REXML gems from 3.3.3 to 3.4.1 have a DoS vulnerability when parsing XML containing multiple XML declarations: https://www.ruby-lang.org/en/news/2025/09/18/dos-rexml-cve-2025-58767/
We are currently using Fastlane that depends on this gem.