Bump rexml from 3.2.6 to 3.2.8 (#21)

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.6 to 3.2.8.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.6...v3.2.8)

---
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>

Gemfile.lock

@@ -11,8 +11,10 @@ GEM
       with_env (= 1.1.0)
       xml-simple (~> 1.1.9)
     racc (1.7.3)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rubyzip (2.3.2)
+    strscan (3.1.0)
     thor (1.3.1)
     tomlrb (2.0.3)
     with_env (1.1.0)