Build(deps-dev): 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] <[email protected]>

Author: dependabot[bot]

Gemfile.lock

@@ -176,7 +176,8 @@ GEM
       http-cookie (>= 1.0.2, < 2.0)
       mime-types (>= 1.16, < 4.0)
       netrc (~> 0.8)
-    rexml (3.2.5)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rspec-core (3.12.1)
       rspec-support (~> 3.12.0)
     rspec-expectations (3.12.2)
@@ -227,6 +228,7 @@ GEM
       sprockets (>= 3.0.0)
     sqlite3 (1.6.0)
       mini_portile2 (~> 2.8.0)
+    strscan (3.1.0)
     thor (1.3.1)
     tilt (2.0.11)
     timeout (0.4.1)