Bump rexml from 3.2.6 to 3.2.8

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] <support@github.com>

Gemfile.lock

@@ -173,7 +173,8 @@ GEM
     rainbow (3.1.1)
     rake (13.1.0)
     regexp_parser (2.8.3)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rspec-core (3.9.3)
       rspec-support (~> 3.9.3)
     rspec-expectations (3.9.4)
@@ -228,6 +229,7 @@ GEM
     sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
+    strscan (3.1.0)
     thor (1.3.0)
     timeout (0.4.1)
     tzinfo (2.0.6)