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] <[email protected]>

Gemfile.lock

@@ -47,14 +47,16 @@ GEM
       bigdecimal
     pastel (0.8.0)
       tty-color (~> 0.5)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rubyntlm (0.6.3)
     rubyzip (2.3.2)
     strings (0.2.1)
       strings-ansi (~> 0.2)
       unicode-display_width (>= 1.5, < 3.0)
       unicode_utils (~> 1.4)
     strings-ansi (0.2.0)
+    strscan (3.1.0)
     test-kitchen (3.6.0)
       bcrypt_pbkdf (~> 1.0)
       chef-utils (>= 16.4.35)