[Security] Bump nokogiri from 1.10.7 to 1.10.8 (#1558)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.7 to 1.10.8. **This update includes a security fix.**
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.10.7...v1.10.8)

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

Gemfile.lock

@@ -145,7 +145,7 @@ GEM
     momentjs-rails (2.20.1)
       railties (>= 3.1)
     multipart-post (2.1.1)
-    nokogiri (1.10.7)
+    nokogiri (1.10.8)
       mini_portile2 (~> 2.4.0)
     parser (2.7.0.2)
       ast (~> 2.4.0)