Unignore numpy in version policy

Author: VeckoTheGecko

.github/ci/policy.yaml

@@ -20,7 +20,6 @@ policy:
     - nbval
     - uxarray # undergoes active development
     - xgcm # undergoes active development
-    - numpy # using numpy 2 (TODO: remove ignore after 2024-06-17 )
 
   # these packages don't fail the CI, but will be printed in the report
   ignored_violations: []