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: indirect
...

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

Gemfile.lock

@@ -62,7 +62,8 @@ GEM
     rake (13.2.1)
     rb-readline (0.5.5)
     regexp_parser (2.9.1)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rspec (3.13.0)
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
@@ -98,6 +99,7 @@ GEM
     simplecov-html (0.12.3)
     simplecov-lcov (0.8.0)
     simplecov_json_formatter (0.1.4)
+    strscan (3.1.0)
     unicode-display_width (2.5.0)
     webmock (3.23.0)
       addressable (>= 2.8.0)