Bump nokogiri from 1.15.5 to 1.15.6

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.15.5 to 1.15.6.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.15.5...v1.15.6)

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

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

Gemfile.lock

@@ -11,14 +11,14 @@ GEM
       nokogiri (>= 1.5.0)
       rubyzip (= 0.9.9)
     mini_portile2 (2.8.5)
-    nokogiri (1.15.5)
+    nokogiri (1.15.6)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
-    nokogiri (1.15.5-arm64-darwin)
+    nokogiri (1.15.6-arm64-darwin)
       racc (~> 1.4)
-    nokogiri (1.15.5-x86_64-darwin)
+    nokogiri (1.15.6-x86_64-darwin)
       racc (~> 1.4)
-    nokogiri (1.15.5-x86_64-linux)
+    nokogiri (1.15.6-x86_64-linux)
       racc (~> 1.4)
     racc (1.7.3)
     rake (13.1.0)