support 3.14 in buildpacks preview

Author: glasnt

run/django/cloudmigrate.yaml

@@ -16,7 +16,7 @@
 steps:
   - id: "Build Container Image"
     name: gcr.io/k8s-skaffold/pack
-    args: ["build", "${_IMAGE_NAME}", "--builder=gcr.io/buildpacks/builder"]
+    args: ["build", "${_IMAGE_NAME}", "--builder=gcr.io/buildpacks/builder:google-24"]
 
   - id: "Push Container Image"
     name: "gcr.io/cloud-builders/docker"

run/django/e2e_test_setup.yaml

@@ -70,7 +70,7 @@ steps:
 
   - id: "Build Container Image"
     name: gcr.io/k8s-skaffold/pack
-    args: ["build", "${_IMAGE_NAME}", "--builder=gcr.io/buildpacks/builder",
+    args: ["build", "${_IMAGE_NAME}", "--builder=gcr.io/buildpacks/builder:google-24",
       "--env", "GOOGLE_PYTHON_VERSION=${_PYTHON_VERSION}"]
 
   - id: "Push Container Image"