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

@@ -108,8 +108,10 @@ GEM
       pry (>= 0.13, < 0.15)
     public_suffix (5.0.5)
     rainbow (3.1.1)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     ruby-progressbar (1.13.0)
+    strscan (3.1.0)
     thor (1.3.1)
     toml-rb (2.2.0)
       citrus (~> 3.0, > 3.0)