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: indirect
...

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

Gemfile.lock

@@ -63,12 +63,12 @@ GEM
       rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.3.6)
     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-x64-mingw32)
+    nokogiri (1.15.6-x64-mingw32)
       racc (~> 1.4)
-    nokogiri (1.15.5-x86-mingw32)
+    nokogiri (1.15.6-x86-mingw32)
       racc (~> 1.4)
     nokogumbo (2.0.5)
       nokogiri (~> 1.8, >= 1.8.4)