api: swagger: adjust ContainerWaitResponse error as optional

Signed-off-by: Niel Drummond <niel@drummond.lu>

api/swagger.yaml

@@ -4656,7 +4656,7 @@ definitions:
     type: "object"
     x-go-name: "WaitResponse"
     title: "ContainerWaitResponse"
-    required: [StatusCode, Error]
+    required: [StatusCode]
     properties:
       StatusCode:
         description: "Exit code of the container"

api/types/container/wait_response.go

@@ -10,8 +10,7 @@ package container
 type WaitResponse struct {
 
 	// error
-	// Required: true
-	Error *WaitExitError `json:"Error"`
+	Error *WaitExitError `json:"Error,omitempty"`
 
 	// Exit code of the container
 	// Required: true