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](https://github.com/ruby/rexml/compare/v3.2.5...v3.3.3)

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

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

Gemfile.lock

@@ -404,7 +404,8 @@ GEM
       railties (>= 5.2)
     reverse_markdown (2.1.1)
       nokogiri
-    rexml (3.2.5)
+    rexml (3.3.3)
+      strscan
     rolify (5.3.0)
     rubocop (1.31.2)
       json (~> 2.3)
@@ -478,6 +479,7 @@ GEM
       spring (>= 4)
     ssrf_filter (1.1.2)
     stripe (5.29.0)
+    strscan (3.1.0)
     swd (1.3.0)
       activesupport (>= 3)
       attr_required (>= 0.0.5)