Bump nokogiri from 1.6.6.2 to 1.9.1

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.6.6.2 to 1.9.1.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.6.6.2...v1.9.1)

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

Gemfile.lock

@@ -196,16 +196,16 @@ GEM
       rails (>= 3.2.0)
     method_source (0.8.2)
     mime-types (2.99.3)
-    mini_portile (0.6.2)
+    mini_portile2 (2.4.0)
     minitest (5.12.0)
     modernizr-rails (2.6.2.3)
     multi_json (1.14.1)
     nenv (0.2.0)
     net-scp (1.2.1)
       net-ssh (>= 2.6.5)
     net-ssh (3.1.1)
-    nokogiri (1.6.6.2)
-      mini_portile (~> 0.6.0)
+    nokogiri (1.9.1)
+      mini_portile2 (~> 2.4.0)
     notiffany (0.0.6)
       nenv (~> 0.1)
       shellany (~> 0.0)