ci(alpha): avoid race by cancel non-latest concurrent runs (#1213)

.github/workflows/alpha.yml

@@ -9,6 +9,10 @@ permissions: write-all
 env:
   CARGO_INCREMENTAL: 0
   RUST_BACKTRACE: short
+concurrency:
+  # only allow per workflow per commit (and not pr) to run at a time
+  group: "${{ github.workflow }} - ${{ github.head_ref || github.ref }}"
+  cancel-in-progress: ${{ github.ref != 'refs/heads/main' }}
 
 jobs:
   alpha: