Update rexml requirement from = 3.2.5 to = 3.4.4

Updates the requirements on [rexml](https://github.com/ruby/rexml) to permit the latest version.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.5...v3.4.4)

---
updated-dependencies:
- dependency-name: rexml
  dependency-version: 3.4.4
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

next_rails.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "simplecov", "~> 0.17.1"
   spec.add_development_dependency "timecop", "~> 0.9.1"
   spec.add_development_dependency "byebug"
-  spec.add_development_dependency "rexml", "3.2.5" # limited on purpose, new versions don't work with old rubies
+  spec.add_development_dependency "rexml", "3.4.4" # limited on purpose, new versions don't work with old rubies
   spec.add_development_dependency "webmock", "3.16.2"
   spec.add_development_dependency "base64"
 end