chore: remove unimplemented gateway (#2139)

gateway/config.go

@@ -1,7 +0,0 @@
-package gateway
-
-import "github.com/zeromicro/go-zero/rest"
-
-type GatewayConf struct {
-	rest.RestConf
-}

gateway/server.go

@@ -1,6 +0,0 @@
-package gateway
-
-type Server struct {
-}
-
-func MustNewServer() {}