Bump rexml from 3.2.5 to 3.2.8 (#119)

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.5 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@v3.2.5...v3.2.8)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile.lock

@@ -18,7 +18,8 @@ GEM
       rack
     rainbow (3.0.0)
     regexp_parser (2.1.1)
-    rexml (3.2.5)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rspec (3.10.0)
       rspec-core (~> 3.10.0)
       rspec-expectations (~> 3.10.0)
@@ -50,6 +51,7 @@ GEM
       rack (~> 2.2)
       rack-protection (= 2.2.3)
       tilt (~> 2.0)
+    strscan (3.1.0)
     tilt (2.0.11)
     unicode-display_width (2.0.0)
     webrick (1.7.0)