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
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -247,7 +247,8 @@ GEM
       connection_pool
     reline (0.5.7)
       io-console (~> 0.5)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rswag-api (2.13.0)
       activesupport (>= 3.1, < 7.2)
       railties (>= 3.1, < 7.2)
@@ -286,6 +287,7 @@ GEM
       activesupport (>= 5.2)
       sprockets (>= 3.0.0)
     stringio (3.1.0)
+    strscan (3.1.0)
     thor (1.3.1)
     tilt (2.3.0)
     timeout (0.4.1)