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

@@ -143,12 +143,14 @@ GEM
     open4 (1.3.4)
     public_suffix (4.0.6)
     rchardet (1.8.0)
-    rexml (3.2.5)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     ruby-macho (2.5.1)
     ruby2_keywords (0.0.5)
     sawyer (0.8.2)
       addressable (>= 2.3.5)
       faraday (> 0.8, < 2.0)
+    strscan (3.1.0)
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
     typhoeus (1.4.1)