Bump nokogiri from 1.10.8 to 1.13.6

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.8 to 1.13.6.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.10.8...v1.13.6)

---
updated-dependencies:
- dependency-name: nokogiri
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -10,14 +10,16 @@ GEM
     kramdown (2.3.0)
       rexml
     mime-types (1.25.1)
-    mini_portile2 (2.4.0)
+    mini_portile2 (2.8.0)
     multi_json (1.14.1)
     nanoc (3.7.5)
       cri (~> 2.3)
-    nokogiri (1.10.8)
-      mini_portile2 (~> 2.4.0)
+    nokogiri (1.13.6)
+      mini_portile2 (~> 2.8.0)
+      racc (~> 1.4)
     pygments.rb (1.2.1)
       multi_json (>= 1.0.0)
+    racc (1.6.0)
     rack (2.2.3.1)
     rake (12.3.3)
     rexml (3.2.4)