ci: remove multi-threading in nvcc compile flags (#229)

We already created lots of process and there is no need to use
multi-threading to accelerate compilation.

Author: yzh119

python/setup.py

@@ -394,8 +394,6 @@ def __init__(self, *args, **kwargs) -> None:
                 "nvcc": [
                     "-O3",
                     "-std=c++17",
-                    "--threads",
-                    "8",
                     "-Xfatbin",
                     "-compress-all",
                 ],