chore(deps): bump rexml from 3.3.6 to 3.3.9

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]>

Gemfile.lock

@@ -485,8 +485,7 @@ GEM
     responders (3.1.1)
       actionpack (>= 5.2)
       railties (>= 5.2)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     rouge (4.3.0)
     rqrcode (2.2.0)
       chunky_png (~> 1.0)
@@ -570,7 +569,6 @@ GEM
     stimulus-rails (1.3.4)
       railties (>= 6.0.0)
     stringio (3.1.1)
-    strscan (3.1.0)
     swd (2.0.3)
       activesupport (>= 3)
       attr_required (>= 0.0.5)