fix: merge queue auto-cancelling when >1 entry... (#2558)

Author: haakonvt

.github/workflows/build.yml

@@ -6,7 +6,7 @@ on:
   pull_request:
 
 concurrency:
-  group: pr-${{ github.workflow }}-${{ github.head_ref }}
+  group: pr-${{ github.workflow }}-${{ github.head_ref || github.ref }}
   cancel-in-progress: true
 
 jobs: