Support cancelling PR workflows when new commit is pushed

Author: ktbarrett

.github/workflows/tests.yml

@@ -274,3 +274,7 @@ jobs:
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           verbose: true
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ contains(github.ref, 'master') }}