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

@@ -58,7 +58,8 @@ GEM
       method_source (~> 1.0)
     rainbow (3.0.0)
     regexp_parser (2.0.3)
-    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)
@@ -97,6 +98,7 @@ GEM
       unicode-display_width (~> 1.5)
       unicode_utils (~> 1.4)
     strings-ansi (0.2.0)
+    strscan (3.1.0)
     test-kitchen (2.10.0)
       bcrypt_pbkdf (~> 1.0)
       ed25519 (~> 1.2)