Bump nokogiri from 1.12.5 to 1.13.6

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.12.5 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@v1.12.5...v1.13.6)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -88,7 +88,9 @@ GEM
       rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.4.0)
     multipart-post (2.1.1)
-    nokogiri (1.12.5-x86_64-darwin)
+    nokogiri (1.13.6-x86_64-darwin)
+      racc (~> 1.4)
+    nokogiri (1.13.6-x86_64-linux)
       racc (~> 1.4)
     nokogumbo (2.0.5)
       nokogiri (~> 1.8, >= 1.8.4)
@@ -99,7 +101,7 @@ GEM
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     public_suffix (4.0.6)
-    racc (1.5.2)
+    racc (1.6.0)
     rainbow (3.0.0)
     rb-fsevent (0.11.0)
     rb-inotify (0.10.1)
@@ -122,6 +124,7 @@ GEM
 
 PLATFORMS
   x86_64-darwin-19
+  x86_64-linux
 
 DEPENDENCIES
   html-proofer