kpack is no longer optional under kubernetes

This has been the case for some time, but was not reflected in the
config schema

[#173630293]

Authored-by: Matt Royal <mroyal@pivotal.io>

Author: matt-royal

lib/cloud_controller/config_schemas/api_schema.rb

@@ -372,7 +372,7 @@ class ApiSchema < VCAP::Config
             },
             ca_file: String,
             workloads_namespace: String,
-            optional(:kpack) => { # TODO: this isn't optional in practice
+            kpack: {
               builder_namespace: String,
               registry_service_account_name: String,
               registry_tag_base: String,

lib/cloud_controller/config_schemas/worker_schema.rb

@@ -179,7 +179,7 @@ class WorkerSchema < VCAP::Config
             },
             ca_file: String,
             workloads_namespace: String,
-            optional(:kpack) => {
+            kpack: {
               builder_namespace: String,
               registry_service_account_name: String,
               registry_tag_base: String,