Bump rexml from 3.2.6 to 3.3.9 in /bootstrap

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.6 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@v3.2.6...v3.3.9)

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

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

bootstrap/Gemfile.lock

@@ -21,7 +21,7 @@ GEM
     regexp_parser (2.8.3)
     reline (0.3.1)
       io-console (~> 0.5)
-    rexml (3.2.6)
+    rexml (3.3.9)
     rubocop (1.59.0)
       json (~> 2.3)
       language_server-protocol (>= 3.17.0)