Bump rexml from 3.2.5 to 3.2.8

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.5 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@v3.2.5...v3.2.8)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -22,7 +22,8 @@ GEM
     rdoc (6.4.1.1)
       psych (>= 4.0.0)
     regexp_parser (2.5.0)
-    rexml (3.2.5)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rspec (3.11.0)
       rspec-core (~> 3.11.0)
       rspec-expectations (~> 3.11.0)
@@ -63,6 +64,7 @@ GEM
     simplecov-lcov (0.8.0)
     simplecov_json_formatter (0.1.4)
     stringio (3.0.6)
+    strscan (3.1.0)
     test-unit (3.5.3)
       power_assert
     unicode-display_width (2.1.0)