chore(deps-dev): bump rexml in /fluent-plugin-enhance-k8s-metadata (#639

)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

fluent-plugin-enhance-k8s-metadata/Gemfile.lock

@@ -93,12 +93,14 @@ GEM
     public_suffix (5.0.4)
     rake (13.2.1)
     recursive-open-struct (1.1.3)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     ruby2_keywords (0.0.5)
     serverengine (2.3.2)
       sigdump (~> 0.2.2)
     sigdump (0.2.5)
     strptime (0.2.5)
+    strscan (3.1.0)
     test-unit (3.6.2)
       power_assert
     tzinfo (2.0.4)