Bump rexml from 3.3.6 to 3.3.9

Bumps [rexml](https://github.com/ruby/rexml) from 3.3.6 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@v3.3.6...v3.3.9)

---
updated-dependencies:
- dependency-name: rexml
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Gemfile

@@ -34,7 +34,7 @@ gem 'rack', '>= 2.2.8.1'
 gem 'rack-cors', require: 'rack/cors' # CORS
 gem 'rails-html-sanitizer', '>= 1.4.4'
 gem 'rainbow'
-gem 'rexml', '~> 3.3.6'
+gem 'rexml', '~> 3.3.9'
 gem 'roo', '~> 2.10'
 gem 'roo-xls', '~> 1.2'
 gem 'ruby-saml'

Gemfile.lock

@@ -376,8 +376,7 @@ GEM
     responders (3.1.1)
       actionpack (>= 5.2)
       railties (>= 5.2)
-    rexml (3.3.6)
-      strscan
+    rexml (3.3.9)
     roo (2.10.1)
       nokogiri (~> 1)
       rubyzip (>= 1.3.0, < 3.0.0)
@@ -491,7 +490,6 @@ GEM
     stringio (3.1.1)
     strong_migrations (1.8.0)
       activerecord (>= 5.2)
-    strscan (3.1.0)
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
     terser (1.2.4)
@@ -580,7 +578,7 @@ DEPENDENCIES
   rails-controller-testing
   rails-html-sanitizer (>= 1.4.4)
   rainbow
-  rexml (~> 3.3.6)
+  rexml (~> 3.3.9)
   roo (~> 2.10)
   roo-xls (~> 1.2)
   rspec-rails