Bump nokogiri from 1.10.4 to 1.13.4

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.4 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@v1.10.4...v1.13.4)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -90,18 +90,20 @@ GEM
       rb-inotify (>= 0.9)
     maruku (0.7.0)
     mercenary (0.3.5)
-    mini_portile2 (2.4.0)
+    mini_portile2 (2.8.0)
     minitest (5.5.1)
     net-dns (0.8.0)
-    nokogiri (1.10.4)
-      mini_portile2 (~> 2.4.0)
+    nokogiri (1.13.4)
+      mini_portile2 (~> 2.8.0)
+      racc (~> 1.4)
     parslet (1.5.0)
       blankslate (~> 2.0)
     posix-spawn (0.3.9)
     public_suffix (1.4.6)
     pygments.rb (0.6.1)
       posix-spawn (~> 0.3.6)
       yajl-ruby (~> 1.2.0)
+    racc (1.6.0)
     rb-fsevent (0.9.4)
     rb-inotify (0.9.5)
       ffi (>= 0.5.0)