remove go generate in travis workflow

.travis.yml

@@ -5,7 +5,6 @@ go_import_path: v2ray.com/core
 git:
   depth: 5
 script:
-- go generate v2ray.com/core/...
 - go test -tags json v2ray.com/core/...
 after_success:
 - ./testing/coverage/coverall