Bump nokogiri from 1.8.2 to 1.13.4

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.8.2 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@v1.8.2...v1.13.4)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -79,7 +79,7 @@ GEM
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
     mini_mime (1.0.0)
-    mini_portile2 (2.3.0)
+    mini_portile2 (2.8.0)
     minitest (4.7.5)
     mixlib-authentication (2.0.0)
     mixlib-config (2.2.6)
@@ -91,8 +91,9 @@ GEM
     multipart-post (2.0.0)
     mustermann (1.0.2)
     nio4r (2.3.0)
-    nokogiri (1.8.2)
-      mini_portile2 (~> 2.3.0)
+    nokogiri (1.13.4)
+      mini_portile2 (~> 2.8.0)
+      racc (~> 1.4)
     oj (3.5.1)
     parallel (1.12.1)
     parser (2.5.1.0)