ci: fix concurrency group for ci-pr-riscv64-linux workflow

Author: alexrp

.github/workflows/ci-pr-riscv64-linux.yaml

@@ -8,7 +8,7 @@ on:
       - synchronize
 concurrency:
   # Cancels pending runs when a PR gets updated.
-  group: ${{ github.head_ref || github.run_id }}-${{ github.actor }}
+  group: riscv64-linux-${{ github.head_ref || github.run_id }}-${{ github.actor }}
   cancel-in-progress: true
 permissions:
   # Sets permission policy for `GITHUB_TOKEN`