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>

Author: dependabot[bot]

Gemfile.lock

@@ -36,7 +36,8 @@ GEM
     rainbow (3.1.1)
     rake (13.1.0)
     regexp_parser (2.8.0)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rspec (3.13.0)
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
@@ -64,6 +65,7 @@ GEM
       parser (>= 3.2.1.0)
     ruby-progressbar (1.13.0)
     ruby2_keywords (0.0.5)
+    strscan (3.1.0)
     unicode-display_width (2.4.2)
     vcr (6.1.0)
     webmock (3.19.1)