remove defunct NVIDIA installation instructions

README.md

@@ -77,13 +77,4 @@ pip install jupyter
 jupyter notebook ./waveorder/examples/
 ```
 
-(Optional) Use NVIDIA GPUs by installing `cupy` with [these instructions](https://docs.cupy.dev/en/stable/install.html). Check that `cupy` is properly installed with
-
-```sh
-python
->>> import cupy
-```
-
-To use GPUs in `waveorder` set ```use_gpu=True``` when initializing the simulator and reconstructor classes.
-
 (M1 users) `pytorch` has [incomplete GPU support](https://github.com/pytorch/pytorch/issues/77764), so please use `export PYTORCH_ENABLE_MPS_FALLBACK=1` to fallback to CPU.