build(deps): bump rexml from 3.3.6 to 3.3.8

Bumps [rexml](https://github.com/ruby/rexml) from 3.3.6 to 3.3.8.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.3.6...v3.3.8)

---
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

@@ -426,8 +426,7 @@ GEM
     responders (3.1.1)
       actionpack (>= 5.2)
       railties (>= 5.2)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.8)
     rspec-core (3.13.1)
       rspec-support (~> 3.13.0)
     rspec-expectations (3.13.3)
@@ -537,7 +536,6 @@ GEM
     stringio (3.1.1)
     strong_migrations (2.0.0)
       activerecord (>= 6.1)
-    strscan (3.1.0)
     thor (1.3.2)
     timeout (0.4.1)
     traceroute (0.8.1)