docs: resolve broken link

referenced a repo that did not exist.  easy fix is list of "cool-" cisagov repositories.   
Could not find reference to COOL on CISA website for better link, but did note acronym collision with https://www.cool.osd.mil/ program

README.md

@@ -40,7 +40,7 @@ Our development team is responsible for a majority of the repositories in the
 [cisagov organization](https://github.com/cisagov). Take a look around to get a
 sense of what we're currently working on.  Recently we've been making a big
 push to cloudify all the things, resulting in our new
-[COOL](https://github.com/cisagov/cool-system) system. You'll find a good deal
+[COOL](https://github.com/search?q=org%3Acisagov+%22cool-%22&type=repositories) system. You'll find a good deal
 of Python, infrastructure as code (Terraform, Ansible, Packer), and old-school
 shell scripting.