Bump rexml from 3.3.6 to 3.3.9 (#438)

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>

Gemfile.lock

@@ -246,8 +246,7 @@ GEM
     regexp_parser (2.9.2)
     reline (0.5.10)
       io-console (~> 0.5)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     rouge (4.4.0)
     rubocop-ast (1.31.3)
       parser (>= 3.3.1.0)
@@ -263,7 +262,6 @@ GEM
     stimulus-rails (1.3.4)
       railties (>= 6.0.0)
     stringio (3.1.1)
-    strscan (3.1.0)
     syntax_tree (6.2.0)
       prettier_print (>= 1.2.0)
     thor (1.3.2)