Remove snippets directory #959

Job	Run time
CMake build on MacOS	6m 25s
CMake Serial Minimal Build on Linux	1m 11s
CMake Serial With Clawpack Build on Linux	9m 34s
CMake Serial With Clawpack and HDF Build on Linux	10m 55s
CMake Serial With GeoClaw Build on Linux	4m 1s
CMake Serial With CudaClaw (CUDA 10.1) Build on Linux	2m 39s
CMake Serial With CudaClaw (CUDA 11.3) Build on Linux	3m 29s
CMake MPI Minimal Build on Linux	2m 14s
CMake MPI With Clawpack Build on Linux	8m 39s
CMake MPI With Clawpack and HDF Build on Linux	10m 27s
CMake MPI With GeoClaw Build on Linux	4m 8s
CMake MPI With CudaClaw (CUDA 10.1) Build on Linux	2m 44s
CMake MPI With CudaClaw (CUDA 11.3) Build on Linux	3m 46s
CMake MPI With ThunderEgg Build on Linux	4m 4s
	1h 14m 16s

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