Merge pull request #1009 from cmu-delphi/dependabot/bundler/docs/nokogiri-1.13.9

Bump nokogiri from 1.13.6 to 1.13.9 in /docs

Author: krivard

docs/Gemfile.lock

@@ -211,7 +211,7 @@ GEM
       jekyll-seo-tag (~> 2.1)
     minitest (5.14.4)
     multipart-post (2.1.1)
-    nokogiri (1.13.6)
+    nokogiri (1.13.9)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
     octokit (4.20.0)