Bump rexml from 3.2.8 to 3.3.3

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.8 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@v3.2.8...v3.3.3)

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

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -55,8 +55,8 @@ GEM
     rb-fsevent (0.11.0)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rexml (3.2.8)
-      strscan (>= 3.0.9)
+    rexml (3.3.3)
+      strscan
     rouge (3.26.1)
     safe_yaml (1.0.5)
     sassc (2.4.0)