Bump nokogiri from 1.8.2 to 1.10.4 in /docs (#1007)

Bumps [nokogiri](https://github.com/sparklemotion/nokogiri) from 1.8.2 to 1.10.4.
- [Release notes](https://github.com/sparklemotion/nokogiri/releases)
- [Changelog](https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md)
- [Commits](sparklemotion/nokogiri@v1.8.2...v1.10.4)

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

docs/Gemfile.lock

@@ -201,16 +201,16 @@ GEM
       rb-inotify (~> 0.9, >= 0.9.7)
       ruby_dep (~> 1.2)
     mercenary (0.3.6)
-    mini_portile2 (2.3.0)
+    mini_portile2 (2.4.0)
     minima (2.4.1)
       jekyll (~> 3.5)
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
     minitest (5.11.3)
     multipart-post (2.0.0)
     net-dns (0.8.0)
-    nokogiri (1.8.2)
-      mini_portile2 (~> 2.3.0)
+    nokogiri (1.10.4)
+      mini_portile2 (~> 2.4.0)
     octokit (4.8.0)
       sawyer (~> 0.8.0, >= 0.5.3)
     pathutil (0.16.1)