Bump rexml from 3.3.6 to 3.3.9 in /test/using_bundler (#128)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

test/using_bundler/Gemfile.lock

@@ -11,8 +11,7 @@ GEM
     racc (1.8.0)
     rainbow (3.1.1)
     regexp_parser (2.9.2)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     rubocop (1.65.0)
       json (~> 2.3)
       language_server-protocol (>= 3.17.0)
@@ -27,7 +26,6 @@ GEM
     rubocop-ast (1.31.3)
       parser (>= 3.3.1.0)
     ruby-progressbar (1.13.0)
-    strscan (3.1.0)
     unicode-display_width (2.5.0)
 
 PLATFORMS