update gcb-docker-gcloud to latest, and pin digest

this is a staging repository, which has lower security than registry.k8s.io, so we should REALLY be pinning it.

TODO: This is one of the few places we still depend on GCR to build things. We should consider promoting this image to registry.k8s.io or using a different image.

build/dependencies.yaml

@@ -271,7 +271,7 @@ dependencies:
 
   # GCB docker gcloud image
   - name: "gcb-docker-gcloud: dependents"
-    version: v20230623-56e06d7c18
+    version: v20240523-a15ad90fc9@sha256:bb04162508c2c61637eae700a0d8e8c8be8f2d4c831d2b75e59db2d4dd6cf75d
     refPaths:
     - path: build/pause/cloudbuild.yaml
       match: gcr.io/k8s-staging-test-infra/gcb-docker-gcloud

build/pause/cloudbuild.yaml

@@ -4,7 +4,7 @@ options:
   substitution_option: ALLOW_LOOSE
   machineType: 'N1_HIGHCPU_8'
 steps:
-  - name: 'gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:v20230623-56e06d7c18'
+  - name: 'gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:v20240523-a15ad90fc9@sha256:bb04162508c2c61637eae700a0d8e8c8be8f2d4c831d2b75e59db2d4dd6cf75d'
     entrypoint: 'bash'
     dir: ./build/pause
     env:

cluster/images/etcd/cloudbuild.yaml

@@ -4,7 +4,7 @@ options:
   substitution_option: ALLOW_LOOSE
   machineType: 'N1_HIGHCPU_8'
 steps:
-  - name: 'gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:v20230623-56e06d7c18'
+  - name: 'gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:v20240523-a15ad90fc9@sha256:bb04162508c2c61637eae700a0d8e8c8be8f2d4c831d2b75e59db2d4dd6cf75d'
     entrypoint: 'bash'
     dir: ./cluster/images/etcd
     env:

test/images/cloudbuild.yaml

@@ -9,7 +9,7 @@ options:
   substitution_option: ALLOW_LOOSE
   machineType: 'N1_HIGHCPU_8'
 steps:
-  - name: 'gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:v20230623-56e06d7c18'
+  - name: 'gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:v20240523-a15ad90fc9@sha256:bb04162508c2c61637eae700a0d8e8c8be8f2d4c831d2b75e59db2d4dd6cf75d'
     entrypoint: 'bash'
     dir: ./test/images/
     env: