add ValueError for legacy dask-dataframe when dask_cuda is imported #588

Job	Run time
checks / check-style	1m 8s
wheel-build / compute-matrix	3s
checks / other-checks	36s
wheel-build / 12.5.1, 3.12, amd64, rockylinux8	3m 24s
conda-python-build / compute-matrix	2s
conda-python-build / 11.8.0, 3.10, amd64, rockylinux8	3m 30s
conda-python-build / 12.5.1, 3.10, amd64, rockylinux8	3m 37s
conda-python-build / 11.8.0, 3.11, amd64, rockylinux8	3m 35s
conda-python-build / 12.5.1, 3.11, amd64, rockylinux8	3m 17s
conda-python-build / 11.8.0, 3.12, amd64, rockylinux8	3m 16s
conda-python-build / 12.5.1, 3.12, amd64, rockylinux8	3m 18s
conda-python-build / 11.8.0, 3.10, arm64, rockylinux8	2m 48s
conda-python-build / 12.5.1, 3.10, arm64, rockylinux8	2m 59s
conda-python-build / 11.8.0, 3.11, arm64, rockylinux8	2m 50s
conda-python-build / 12.5.1, 3.11, arm64, rockylinux8	2m 50s
conda-python-build / 11.8.0, 3.12, arm64, rockylinux8	2m 49s
conda-python-build / 12.5.1, 3.12, arm64, rockylinux8	2m 42s
docs-build / build	4m 28s
conda-python-tests / compute-matrix	3s
conda-python-tests / 11.8.0, 3.10, amd64, rockylinux8, v100, earliest-driver, oldest-deps	43m 20s
conda-python-tests / 12.5.1, 3.12, amd64, ubuntu24.04, v100, latest-driver, latest-deps	52m 26s
conda-python-tests / 12.0.1, 3.11, arm64, ubuntu20.04, a100, latest-driver, latest-deps	35m 2s
pr-builder / run	1s
	2h 58m 4s

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