Merge pull request #18 from slack-ruby/dependabot/bundler/nokogiri-1.13.9

Bump nokogiri from 1.13.6 to 1.13.9

Author: dblock

Gemfile.lock

@@ -130,7 +130,7 @@ GEM
       slack-ruby-bot (>= 0.10.5)
     newrelic_rpm (6.10.0.364)
     nio4r (2.5.2)
-    nokogiri (1.13.6)
+    nokogiri (1.13.9)
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
     public_suffix (4.0.6)