Bump rexml from 3.3.6 to 3.3.9 in the bundler group

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


Updates `rexml` from 3.3.6 to 3.3.9
- [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/v3.3.6...v3.3.9)

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

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

Gemfile.lock

@@ -72,8 +72,7 @@ GEM
     regexp_parser (2.6.2)
     reverse_markdown (2.1.1)
       nokogiri
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     rubocop (1.45.1)
       json (~> 2.3)
       parallel (~> 1.10)
@@ -104,7 +103,6 @@ GEM
     sawyer (0.9.2)
       addressable (>= 2.3.5)
       faraday (>= 0.17.3, < 3)
-    strscan (3.1.0)
     thor (1.3.2)
     tomlrb (2.0.3)
     tzinfo (2.0.6)