Bump nokogiri from 1.13.6 to 1.15.4

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.13.6 to 1.15.4.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.13.6...v1.15.4)

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

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

Author: dependabot[bot]

Gemfile.lock

@@ -245,13 +245,11 @@ GEM
       jekyll-seo-tag (~> 2.1)
     minitest (5.17.0)
     multipart-post (2.1.1)
-    nokogiri (1.13.9-arm64-darwin)
+    nokogiri (1.15.4-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.13.9-x86_64-darwin)
+    nokogiri (1.15.4-x86_64-darwin)
       racc (~> 1.4)
-    nokogiri (1.13.9-x86_64-linux)
-      racc (~> 1.4)
-    nokogiri (1.13.6-x86_64-linux)
+    nokogiri (1.15.4-x86_64-linux)
       racc (~> 1.4)
     octokit (4.22.0)
       faraday (>= 0.9)
@@ -262,7 +260,7 @@ GEM
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     public_suffix (4.0.7)
-    racc (1.6.0)
+    racc (1.7.1)
     rainbow (3.1.1)
     rb-fsevent (0.11.1)
     rb-inotify (0.10.1)