Bump rexml from 3.3.9 to 3.4.2

Bumps [rexml](https://github.com/ruby/rexml) from 3.3.9 to 3.4.2.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.3.9...v3.4.2)

---
updated-dependencies:
- dependency-name: rexml
  dependency-version: 3.4.2
  dependency-type: indirect
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -249,7 +249,7 @@ GEM
       trailblazer-option (>= 0.1.1, < 0.2.0)
       uber (< 0.2.0)
     retriable (3.1.2)
-    rexml (3.3.9)
+    rexml (3.4.2)
     rouge (2.0.7)
     ruby-macho (2.5.1)
     ruby2_keywords (0.0.5)