workflow: Cancel running deployment when pushing

Author: rdb

.github/workflows/deploy.yml

@@ -7,6 +7,9 @@ jobs:
   build:
     name: Build
     runs-on: ubuntu-latest
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.ref }}
+      cancel-in-progress: true
     steps:
     - uses: actions/checkout@v1
     - uses: actions/setup-python@v1