remove US scope

Author: Courtney Claessens

CONTRIBUTING.md

@@ -8,7 +8,7 @@ Want to contribute? Here are a few guidelines to following:
 
 ## Public domain
 
-This project is in the public domain within the United States, and
+This project is in the public domain and
 copyright and related rights in the work worldwide are waived through
 the [CC0 1.0 Universal public domain dedication](https://creativecommons.org/publicdomain/zero/1.0/).