[Security] Bump nokogiri from 1.8.4 to 1.8.5 (mastodon#8881)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.8.4 to 1.8.5. **This update includes security fixes.**
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.8.4...v1.8.5)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Gemfile.lock

@@ -347,7 +347,7 @@ GEM
       net-ssh (>= 2.6.5)
     net-ssh (4.2.0)
     nio4r (2.3.1)
-    nokogiri (1.8.4)
+    nokogiri (1.8.5)
       mini_portile2 (~> 2.3.0)
     nokogumbo (1.5.0)
       nokogiri