Bump nokogiri from 1.10.4 to 1.10.8 in /docs

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>

docs/Gemfile.lock

@@ -208,9 +208,9 @@ GEM
       jekyll-seo-tag (~> 2.1)
     minitest (5.12.2)
     multipart-post (2.1.1)
-    nokogiri (1.10.4)
+    nokogiri (1.10.8)
       mini_portile2 (~> 2.4.0)
-    nokogiri (1.10.4-x64-mingw32)
+    nokogiri (1.10.8-x64-mingw32)
       mini_portile2 (~> 2.4.0)
     octokit (4.14.0)
       sawyer (~> 0.8.0, >= 0.5.3)
@@ -244,7 +244,6 @@ GEM
     tzinfo-data (1.2019.3)
       tzinfo (>= 1.0.0)
     unicode-display_width (1.6.0)
-    wdm (0.1.1)
 
 PLATFORMS
   ruby
@@ -253,7 +252,6 @@ PLATFORMS
 DEPENDENCIES
   github-pages
   tzinfo-data
-  wdm (~> 0.1.0)
 
 BUNDLED WITH
    2.0.2