Bump nokogiri from 1.18.4 to 1.18.8 in /docker-images/buildbox (#31)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.18.4 to 1.18.8.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/main/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.18.4...v1.18.8)

---
updated-dependencies:
- dependency-name: nokogiri
  dependency-version: 1.18.8
  dependency-type: indirect
...

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Author: dependabot[bot]

docker-images/buildbox/Gemfile.lock

@@ -7,7 +7,7 @@ GEM
       nokogiri (>= 1.4.0)
       sqlite3
     net-http-persistent (2.9.4)
-    nokogiri (1.18.4)
+    nokogiri (1.18.8)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
     paint (0.9.0)