Build(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](ruby/rexml@v3.2.6...v3.2.8)

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

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

Gemfile.lock

@@ -443,7 +443,8 @@ GEM
     request_store (1.5.1)
       rack (>= 1.4)
     retriable (3.1.2)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rolify (6.0.1)
     rotp (6.3.0)
     rspec-activemodel-mocks (1.2.0)
@@ -527,6 +528,7 @@ GEM
       sprockets (>= 3.0.0)
     statistics2 (0.54)
     stripe (5.55.0)
+    strscan (3.1.0)
     syck (1.4.1)
     syslog_protocol (0.9.2)
     text (1.3.1)