Bump rexml from 3.2.5 to 3.3.3

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.5 to 3.3.3.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.5...v3.3.3)

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

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

Gemfile.lock

@@ -65,7 +65,8 @@ GEM
       loofah (~> 2.19, >= 2.19.1)
     rainbow (3.1.1)
     regexp_parser (2.6.0)
-    rexml (3.2.5)
+    rexml (3.3.3)
+      strscan
     rspec (3.12.0)
       rspec-core (~> 3.12.0)
       rspec-expectations (~> 3.12.0)
@@ -101,6 +102,7 @@ GEM
     sinatra-param (1.6.0)
       sinatra (>= 1.3)
     smart_properties (1.17.0)
+    strscan (3.1.0)
     sucker_punch (3.1.0)
       concurrent-ruby (~> 1.0)
     tilt (2.0.11)