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](ruby/rexml@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

@@ -86,10 +86,8 @@ GEM
     netrc (0.11.0)
     nkf (0.2.0)
     public_suffix (4.0.7)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     ruby-macho (2.5.1)
-    strscan (3.1.0)
     typhoeus (1.4.1)
       ethon (>= 0.9.0)
     tzinfo (2.0.6)