updated CI (#484)

Author: lucaferranti

.github/workflows/CI.yml

@@ -11,8 +11,7 @@ jobs:
       fail-fast: false
       matrix:
         version:
-          - '1.5'
-          - '^1.6.0-0'
+          - '1'
           - 'nightly'
         os:
           - ubuntu-latest