Bump nokogiri from 1.5.6 to 1.13.4

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.5.6 to 1.13.4.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/v1.13.4/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.5.6...v1.13.4)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -64,16 +64,8 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.6.1)
-    columnize (0.3.6)
     database_cleaner (0.9.1)
     debug_inspector (0.0.2)
-    debugger (1.4.0)
-      columnize (>= 0.3.1)
-      debugger-linecache (~> 1.1.1)
-      debugger-ruby_core_source (~> 1.2.0)
-    debugger-linecache (1.1.2)
-      debugger-ruby_core_source (>= 1.1.1)
-    debugger-ruby_core_source (1.2.0)
     diff-lcs (1.2.1)
     erubis (2.7.0)
     execjs (1.4.0)
@@ -123,6 +115,7 @@ GEM
       railties
     method_source (0.8.1)
     mime-types (1.21)
+    mini_portile2 (2.8.0)
     multi_json (1.6.1)
     mysql2 (0.3.11)
     net-scp (1.1.0)
@@ -132,12 +125,15 @@ GEM
     net-ssh (2.6.6)
     net-ssh-gateway (1.2.0)
       net-ssh (>= 2.6.5)
-    nokogiri (1.5.6)
+    nokogiri (1.13.4)
+      mini_portile2 (~> 2.8.0)
+      racc (~> 1.4)
     polyglot (0.3.3)
     pry (0.9.12)
       coderay (~> 1.0.5)
       method_source (~> 0.8)
       slop (~> 3.4)
+    racc (1.6.0)
     rack (1.4.5)
     rack-cache (1.2)
       rack (>= 0.4)
@@ -236,7 +232,6 @@ DEPENDENCIES
   capybara (~> 2.0.2)
   coffee-rails (~> 3.2.1)
   database_cleaner (~> 0.9.1)
-  debugger
   factory_girl_rails (~> 4.2.1)
   faker (~> 1.1.2)
   guard-rspec (~> 2.5.0)