Bump nokogiri from 1.10.4 to 1.10.8

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.10.4 to 1.10.8.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sparklemotion/nokogiri/compare/v1.10.4...v1.10.8)

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

Gemfile.lock

@@ -87,7 +87,7 @@ GEM
     mini_portile2 (2.4.0)
     minitest (5.11.3)
     nio4r (2.5.1)
-    nokogiri (1.10.4)
+    nokogiri (1.10.8)
       mini_portile2 (~> 2.4.0)
     parallel (1.17.0)
     parser (2.6.4.0)