chore(deps): 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](https://github.com/ruby/rexml/compare/v3.2.6...v3.2.8)

---
updated-dependencies:
- dependency-name: rexml
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -600,7 +600,8 @@ GEM
     responders (3.1.1)
       actionpack (>= 5.2)
       railties (>= 5.2)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     roadie (5.2.1)
       css_parser (~> 1.4)
       nokogiri (~> 1.15)
@@ -758,6 +759,7 @@ GEM
     stringex (2.8.6)
     stringio (3.1.0)
     stripe (11.1.0)
+    strscan (3.1.0)
     swd (2.0.3)
       activesupport (>= 3)
       attr_required (>= 0.0.5)