Build(deps): Bump rexml from 3.3.8 to 3.3.9

Bumps [rexml](https://github.com/ruby/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
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -444,7 +444,7 @@ GEM
     request_store (1.5.1)
       rack (>= 1.4)
     retriable (3.1.2)
-    rexml (3.3.8)
+    rexml (3.3.9)
     rolify (6.0.1)
     rotp (6.3.0)
     rspec-activemodel-mocks (1.2.1)