remove 1.20 env files #1807

Job	Run time
checks / other-checks	39s
devcontainer / build (amd64, 12.0, conda)	6m 29s
devcontainer / build (amd64, 12.0, pip)	10m 58s
checks / check-style	1m 23s
conda-cpp-build / compute-matrix	3s
clang-tidy / build	4m 22s
wheel-build-cuml / compute-matrix	7s
conda-cpp-build / build (11.8.0, ubuntu22.04, amd64, 3.10)	24m 6s
conda-cpp-build / build (11.8.0, ubuntu22.04, arm64, 3.10)	24m 4s
conda-cpp-build / build (12.2.2, ubuntu22.04, amd64, 3.10)	7m 17s
conda-cpp-build / build (12.2.2, ubuntu22.04, arm64, 3.10)	6m 57s
wheel-build-cuml / 11.8.0, 3.9, amd64, centos7	12m 13s
wheel-build-cuml / 11.8.0, 3.10, amd64, centos7	12m 18s
wheel-build-cuml / 11.8.0, 3.9, arm64, rockylinux8	12m 22s
wheel-build-cuml / 11.8.0, 3.10, arm64, rockylinux8	12m 25s
wheel-build-cuml / 12.2.2, 3.9, amd64, centos7	12m 20s
wheel-build-cuml / 12.2.2, 3.10, amd64, centos7	12m 22s
wheel-build-cuml / 12.2.2, 3.9, arm64, rockylinux8	12m 11s
wheel-build-cuml / 12.2.2, 3.10, arm64, rockylinux8	12m 17s
wheel-tests-cuml	0s
conda-cpp-tests	0s
conda-python-build	0s
conda-python-tests-dask	0s
conda-python-tests-singlegpu	0s
conda-notebook-tests	0s
docs-build	0s
pr-builder	0s
	3h 4m 53s

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