Bump rexml from 3.3.7 to 3.3.9 in the bundler group

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


Updates `rexml` from 3.3.7 to 3.3.9
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.3.7...v3.3.9)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -287,7 +287,7 @@ GEM
     responders (3.1.1)
       actionpack (>= 5.2)
       railties (>= 5.2)
-    rexml (3.3.7)
+    rexml (3.3.9)
     rspec-core (3.13.2)
       rspec-support (~> 3.13.0)
     rspec-expectations (3.13.3)