Update vendor files to point to kubernetes-1.12.0-beta.1

vendor/k8s.io/apimachinery/pkg/runtime/extension.go

@@ -32,7 +32,7 @@ func (re *RawExtension) UnmarshalJSON(in []byte) error {
 	return nil
 }
 
-// Marshal may get called on pointers or values, so implement MarshalJSON on value.
+// MarshalJSON may get called on pointers or values, so implement MarshalJSON on value.
 // http://stackoverflow.com/questions/21390979/custom-marshaljson-never-gets-called-in-go
 func (re RawExtension) MarshalJSON() ([]byte, error) {
 	if re.Raw == nil {