ci: fix two PRs with same branch name but different forks canceling each other

Author: Firestar99

.github/workflows/ci.yaml

@@ -9,7 +9,7 @@ name: CI
 
 # Cancel PR actions on new commits
 concurrency:
-  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
   cancel-in-progress: true
 
 jobs: