fix examples

Author: stanislav-shchetinin

.github/workflows/examples.yaml

@@ -8,7 +8,7 @@ on:
     branches:
       - main
 concurrency:
-  group: examples-${{ github.ref }}-${{ matrix.ydb-version }}
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
   cancel-in-progress: true
 jobs:      
   main: