Bump rexml from 3.2.4 to 3.2.8

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.4 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@v3.2.4...v3.2.8)

---
updated-dependencies:
- dependency-name: rexml
  dependency-type: indirect
...

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

Gemfile.lock

@@ -25,7 +25,8 @@ GEM
     rainbow (3.0.0)
     rake (13.0.1)
     regexp_parser (1.7.1)
-    rexml (3.2.4)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rubocop (0.85.1)
       parallel (~> 1.10)
       parser (>= 2.7.0.1)
@@ -38,6 +39,7 @@ GEM
     rubocop-ast (0.0.3)
       parser (>= 2.7.0.1)
     ruby-progressbar (1.10.1)
+    strscan (3.1.0)
     unicode-display_width (1.7.0)
     webmock (3.12.2)
       addressable (>= 2.3.6)