remove unused headers in secret_create.go

Signed-off-by: allencloud <allen.sun@daocloud.io>

client/secret_create.go

@@ -10,10 +10,8 @@ import (
 
 // SecretCreate creates a new Secret.
 func (cli *Client) SecretCreate(ctx context.Context, secret swarm.SecretSpec) (types.SecretCreateResponse, error) {
-	var headers map[string][]string
-
 	var response types.SecretCreateResponse
-	resp, err := cli.post(ctx, "/secrets/create", nil, secret, headers)
+	resp, err := cli.post(ctx, "/secrets/create", nil, secret, nil)
 	if err != nil {
 		return response, err
 	}