Bump rexml

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


Updates `rexml` from 3.2.6 to 3.3.3
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.6...v3.3.3)

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

Signed-off-by: dependabot[bot] <[email protected]>

examples/middleman/Gemfile.lock

@@ -87,10 +87,12 @@ GEM
     rb-fsevent (0.11.2)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rexml (3.2.6)
+    rexml (3.3.3)
+      strscan
     sassc (2.4.0)
       ffi (~> 1.9)
     servolux (0.13.0)
+    strscan (3.1.0)
     temple (0.10.3)
     thor (1.2.2)
     tilt (2.0.11)