Bump nokogiri from 1.18.3 to 1.18.4 in /docs (#478)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.18.3 to 1.18.4.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.18.3...v1.18.4)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

docs/Gemfile.lock

@@ -97,10 +97,10 @@ GEM
     mercenary (0.4.0)
     mini_portile2 (2.8.8)
     minitest (5.19.0)
-    nokogiri (1.18.3)
+    nokogiri (1.18.4)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
-    nokogiri (1.18.3-x86_64-linux-gnu)
+    nokogiri (1.18.4-x86_64-linux-gnu)
       racc (~> 1.4)
     octokit (4.25.1)
       faraday (>= 1, < 3)