Bump rexml from 3.3.8 to 3.3.9 in the bundler group

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


Updates `rexml` from 3.3.8 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@v3.3.8...v3.3.9)

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

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

Gemfile.lock

@@ -185,7 +185,7 @@ GEM
       trailblazer-option (>= 0.1.1, < 0.2.0)
       uber (< 0.2.0)
     retriable (3.1.2)
-    rexml (3.3.8)
+    rexml (3.3.9)
     rouge (2.0.7)
     ruby2_keywords (0.0.5)
     rubyzip (2.3.2)