Bump rexml from 3.2.8 to 3.3.9

Bumps [rexml](https://github.com/ruby/rexml) from 3.2.8 to 3.3.9.
- [Release notes](https://github.com/ruby/rexml/releases)
- [Changelog](https://github.com/ruby/rexml/blob/master/NEWS.md)
- [Commits](ruby/rexml@v3.2.8...v3.3.9)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -213,8 +213,7 @@ GEM
     regexp_parser (2.7.0)
     reline (0.5.10)
       io-console (~> 0.5)
-    rexml (3.2.8)
-      strscan (>= 3.0.9)
+    rexml (3.3.9)
     rspec-core (3.12.1)
       rspec-support (~> 3.12.0)
     rspec-expectations (3.12.2)
@@ -264,7 +263,6 @@ GEM
     sqlite3 (1.6.2)
       mini_portile2 (~> 2.8.0)
     stringio (3.1.1)
-    strscan (3.1.0)
     tabulo (2.8.2)
       tty-screen (= 0.8.1)
       unicode-display_width (~> 2.2)