Bump rexml from 3.3.5 to 3.3.7

Bumps [rexml](https://github.com/ruby/rexml) from 3.3.5 to 3.3.7.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.3.5...v3.3.7)

---
updated-dependencies:
- dependency-name: rexml
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Gemfile.lock

@@ -70,10 +70,8 @@ GEM
     rainbow (3.1.1)
     rake (13.2.1)
     regexp_parser (2.9.0)
-    rexml (3.3.5)
-      strscan
+    rexml (3.3.7)
     ruby-rc4 (0.1.5)
-    strscan (3.1.0)
     timers (4.3.5)
     ttfunk (1.8.0)
       bigdecimal (~> 3.1)