make sparseml Docker fix conditional (#942)

* remove sparseml Dockerfile cuda temporary error fix

the original error has been fixed (https://github.com/NVIDIA/nvidia-docker/issues/1632) and pulling the latest nvidia cuda ubuntu image and running the fix will produce an error

**test_plan**
build passes locally (second rm command gets a no such file error previously)

* make fix conditional

* command fix

docker/Dockerfile

@@ -7,8 +7,8 @@ FROM nvidia/cuda:${CUDA_VERSION}-devel-ubuntu18.04 as base
 # As of 05/05/22 nvidia images are broken. Two lines below are a temporary fix.
 # Source: https://github.com/NVIDIA/nvidia-docker/issues/1632
 
-RUN rm /etc/apt/sources.list.d/cuda.list
-RUN rm /etc/apt/sources.list.d/nvidia-ml.list
+RUN if [ -f /etc/apt/sources.list.d/cuda.list ] ; then rm /etc/apt/sources.list.d/cuda.list ; fi
+RUN if [ -f /etc/apt/sources.list.d/nvidia-ml.list ] ; then rm /etc/apt/sources.list.d/nvidia-ml.list ; fi
 
 RUN : \
     && apt-get update \