Merge pull request #21063 from cmisenas/fix-guides-warning-env

Fix WARNINGS flag inside guides/Rakefile

guides/Rakefile

@@ -7,7 +7,7 @@ namespace :guides do
 
     desc "Generate HTML guides"
     task :html do
-      ENV["WARN_BROKEN_LINKS"] = "1" # authors can't disable this
+      ENV["WARNINGS"] = "1" # authors can't disable this
       ruby "rails_guides.rb"
     end