Bump rexml from 3.3.6 to 3.3.9 (#864)

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>
Co-authored-by: Paul Doyle <[email protected]>

Gemfile.lock

@@ -387,8 +387,7 @@ GEM
       http-cookie (>= 1.0.2, < 2.0)
       mime-types (>= 1.16, < 4.0)
       netrc (~> 0.8)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     rgeo (3.0.1)
     rgeo-activerecord (7.0.1)
       activerecord (>= 5.0)
@@ -485,7 +484,6 @@ GEM
       activesupport (>= 5.2)
       sprockets (>= 3.0.0)
     stringio (3.1.1)
-    strscan (3.1.0)
     sucker_punch (3.2.0)
       concurrent-ruby (~> 1.0)
     thor (1.3.2)