Bump rexml from 3.2.5 to 3.2.8

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>

Gemfile.lock

@@ -11,7 +11,9 @@ GEM
       rexml
     minitest (5.16.3)
     rake (13.0.6)
-    rexml (3.2.5)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
+    strscan (3.1.0)
 
 PLATFORMS
   ruby