Bump nokogiri from 1.13.4 to 1.13.6 in /docs (#85)

Author: dependabot[bot]

docs/Gemfile.lock

@@ -232,12 +232,12 @@ GEM
       jekyll-seo-tag (~> 2.1)
     minitest (5.15.0)
     multipart-post (2.1.1)
-    nokogiri (1.13.4)
+    nokogiri (1.13.6)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
-    nokogiri (1.13.4-x64-mingw32)
+    nokogiri (1.13.6-x64-mingw32)
       racc (~> 1.4)
-    nokogiri (1.13.4-x86_64-linux)
+    nokogiri (1.13.6-x86_64-linux)
       racc (~> 1.4)
     octokit (4.22.0)
       faraday (>= 0.9)