Bump rexml from 3.3.3 to 3.3.9 in /examples/simple_script

Bumps [rexml](https://github.com/ruby/rexml) from 3.3.3 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@v3.3.3...v3.3.9)

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

Signed-off-by: dependabot[bot] <[email protected]>

examples/simple_script/Gemfile.lock

@@ -10,8 +10,7 @@ GEM
       ast (~> 2.4.1)
     rainbow (3.0.0)
     regexp_parser (2.1.1)
-    rexml (3.3.3)
-      strscan
+    rexml (3.3.9)
     rspec (3.7.0)
       rspec-core (~> 3.7.0)
       rspec-expectations (~> 3.7.0)
@@ -40,7 +39,6 @@ GEM
     rubocop-ast (1.11.0)
       parser (>= 3.0.1.1)
     ruby-progressbar (1.11.0)
-    strscan (3.1.0)
     unicode-display_width (2.1.0)
 
 PLATFORMS