Fix CRD validation error for 'items' field

Signed-off-by: He Xiaoxi <xxhe@alauda.io>

vendor/github.com/go-openapi/spec/header.go

@@ -22,6 +22,10 @@ import (
 	"github.com/go-openapi/swag"
 )
 
+const (
+	jsonArray = "array"
+)
+
 // HeaderProps describes a response header
 type HeaderProps struct {
 	Description string `json:"description,omitempty"`
@@ -57,7 +61,7 @@ func (h *Header) Typed(tpe, format string) *Header {
 
 // CollectionOf a fluent builder method for an array item
 func (h *Header) CollectionOf(items *Items, format string) *Header {
-	h.Type = "array"
+	h.Type = jsonArray
 	h.Items = items
 	h.CollectionFormat = format
 	return h