remove broken link (#350)

portal/contributing.md

@@ -111,8 +111,8 @@ guide for their target repository.
 
 Repo-specific guides can be found in the file named `CONTRIBUTING.md`, located in the top level directory of each repository, or by clicking on the menu item labeled “Contributor’s Guide” found in the rendered content generated by each repository.
 
-Lastly, much of this information has been co-opted from the [GeoCAT
-project](https://geocat.ucar.edu/pages/contributing.html).
+Lastly, much of this information has been co-opted from the GeoCAT
+project](https://geocat.ucar.edu).
 
 ## Ready, set, fork!