Security update rexml

[runephilosof-abtion]

In order to update rexml we need to update the ruby version

Bundler::SolveFailure with message: Could not find compatible versions

Because bundler-audit >= 0.6.1 depends on bundler >= 1.2.0, < 3
  and every version of bundler depends on Ruby >= 3.0.0,
  bundler-audit >= 0.6.1 requires Ruby >= 3.0.0.
So, because Gemfile depends on bundler-audit ~> 0.9.1
  and current Ruby version is = 2.7.2,
  version solving has failed.