tweak deploy test concurrency & fail condition (#66779)

[x-ref](https://github.com/vercel/next.js/actions/runs/9475354204/job/26106589121)

.github/workflows/test_e2e_deploy_release.yml

@@ -47,7 +47,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        group: [1/6, 2/6, 3/6, 4/6, 5/6, 6/6]
+        group: [1/5, 2/5, 3/5, 4/5, 5/5]
     with:
       afterBuild: NEXT_TEST_MODE=deploy NEXT_EXTERNAL_TESTS_FILTERS="test/deploy-tests-manifest.json" node run-tests.js --timings -g ${{ matrix.group }} -c 2 --type e2e
       skipNativeBuild: 'yes'
@@ -79,7 +79,7 @@ jobs:
   report-failure:
     name: report failure to slack
     needs: test-deploy
-    if: ${{ always() && contains(needs.*.result, 'failure') }}
+    if: ${{ always() && (contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')) }}
     runs-on: ubuntu-latest
     steps:
       - name: send webhook