Update cuda_bindings/docs/source/environment_variables.md

Co-authored-by: Leo Fang <leof@nvidia.com>

Author: keenan-simpson

cuda_bindings/docs/source/environment_variables.md

@@ -6,7 +6,7 @@
 
 - `CUDA_PYTHON_PARSER_CACHING` : bool, toggles the caching of parsed header files during the cuda-bindings build process. If caching is enabled (`CUDA_PYTHON_PARSER_CACHING` is True), the cache path is set to ./cache_<library_name>, where <library_name> is derived from the cuda toolkit libraries used to build cuda-bindings.
 
-- `CUDA_PYTHON_PARALLEL_LEVEL` (previously `PARALLEL_LEVEL`) : int, sets the number of threads used in the compilation of cython files. This is passed as the `nthreads` argument to :meth:`cython.cythonize` and as the parallel attribute for building extension modules.
+- `CUDA_PYTHON_PARALLEL_LEVEL` (previously `PARALLEL_LEVEL`) : int, sets the number of threads used in the compilation of extension modules. Not setting it or setting it to 0 would disable parallel builds.
 
 ## Runtime Environment Variables