Bump rexml from 3.2.5 to 3.3.6 in /environments/utility

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.5 to 3.3.6.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.5...v3.3.6)

---
updated-dependencies:
- dependency-name: rexml
  dependency-type: indirect
...

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

environments/utility/Gemfile.lock

@@ -23,7 +23,9 @@ GEM
       insist
       mustache (= 0.99.8)
       stud
-    rexml (3.2.5)
+    rexml (3.3.6)
+      strscan
+    strscan (3.1.0)
     stud (0.0.23)
 
 PLATFORMS