update to smaller machineType

Author: cahillsf

cloudbuild.yaml

@@ -3,7 +3,7 @@
 timeout: 2700s
 options:
   substitution_option: ALLOW_LOOSE
-  machineType: 'E2_HIGHCPU_32'
+  machineType: 'E2_HIGHCPU_8'
 steps:
   - name: 'gcr.io/k8s-staging-test-infra/gcb-docker-gcloud:v20230522-312425ae46'
     entrypoint: make
@@ -12,7 +12,7 @@ steps:
     - TAG=$_GIT_TAG
     - PULL_BASE_REF=$_PULL_BASE_REF
     - DOCKER_BUILDKIT=1
-    args: ['release-staging', '-j', '32', '-O']
+    args: ['release-staging', '-j', '8', '-O']
 substitutions:
   # _GIT_TAG will be filled with a git-based tag for the image, of the form vYYYYMMDD-hash, and
   # can be used as a substitution