Bump rexml from 3.4.1 to 3.4.4

Bumps [rexml](https://github.com/ruby/rexml) from 3.4.1 to 3.4.4.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.4.1...v3.4.4)

---
updated-dependencies:
- dependency-name: rexml
  dependency-version: 3.4.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -460,7 +460,7 @@ GEM
     responders (3.1.1)
       actionpack (>= 5.2)
       railties (>= 5.2)
-    rexml (3.4.1)
+    rexml (3.4.4)
     rouge (4.5.1)
     rspec (3.13.0)
       rspec-core (~> 3.13.0)