[ci] Allow dependency failure for kuberay ci kickoff (#51760)

Kuberay ci kickoff won't happen if the postmerge nightly build and test step fails. The postmerge nightly tests will fail almost all the time, we should still kick off kuberay tests.

Signed-off-by: dayshah <dhyey2019@gmail.com>

Author: dayshah

.buildkite/release-automation/pre_release.rayci.yml

@@ -51,11 +51,22 @@ steps:
         RAYCI_RELEASE: 1
         RAYCI_SCHEDULE: "nightly"
 
+- label: "Check Ray commit in {{matrix}} nightly images"
+  key: check-ray-commit
+  if: build.branch !~ /^releases\// && build.env("RAYCI_WEEKLY_RELEASE_NIGHTLY") == "1"
+  depends_on: trigger-postmerge-nightly
+  allow_dependency_failure: true
+  commands:
+    - bazel run //ci/ray_ci/automation:check_nightly_ray_commit -- --ray_type={{matrix}} --expected_commit="${BUILDKITE_COMMIT}"
+  matrix:
+    - ray
+    - ray-ml
+
   - label: "Trigger :kubernetes: Kuberay CI Tests"
     if: build.env("RAYCI_WEEKLY_RELEASE_NIGHTLY") == "1"
     trigger: "ray-ecosystem-ci-kuberay-ci"
     key: trigger-kuberay
-    depends_on: trigger-postmerge-nightly
+    depends_on: check-ray-commit
     build:
       branch: "release-1.3"
       message: "Triggered by release-automation build #${BUILDKITE_BUILD_NUMBER}"
@@ -125,14 +136,3 @@ steps:
       env:
         AUTOMATIC: 1
         RELEASE_FREQUENCY: "weekly"
-
-  - label: "Check Ray commit in {{matrix}} nightly images"
-    key: check-ray-commit
-    if: build.branch !~ /^releases\// && build.env("RAYCI_WEEKLY_RELEASE_NIGHTLY") == "1"
-    depends_on: trigger-postmerge-nightly
-    allow_dependency_failure: true
-    commands:
-      - bazel run //ci/ray_ci/automation:check_nightly_ray_commit -- --ray_type={{matrix}} --expected_commit="${BUILDKITE_COMMIT}"
-    matrix:
-      - ray
-      - ray-ml