Bump rexml from 3.3.3 to 3.3.6 in the bundler group across 1 directory

Bumps the bundler group with 1 update in the / directory: [rexml](https://github.com/ruby/rexml).


Updates `rexml` from 3.3.3 to 3.3.6
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](https://github.com/ruby/rexml/compare/v3.3.3...v3.3.6)

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

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

Gemfile.lock

@@ -434,7 +434,7 @@ GEM
       actionpack (>= 5.2)
       railties (>= 5.2)
     retriable (3.1.2)
-    rexml (3.3.3)
+    rexml (3.3.6)
       strscan
     rotp (6.3.0)
     rqrcode (2.2.0)