Tests

[MNT] Remove redundant `init`s in `OpenMLTask` descendants by adding ClassVar #1918

Job	Run time
(ubuntu-latest, Py3.8, sk0.23.1, sk-only:false)	3s
docker	4s
(windows-latest, Py, sk0.24.*, sk-only:false)	2s
(ubuntu-latest,Py3.11,sk1.3.*,sk-only:true)	52s
(ubuntu-latest,Py3.10,sk1.6.*,sk-only:true)	50s
(ubuntu-latest,Py3.10,sk1.7.*,sk-only:true)	58s
(ubuntu-latest,Py3.10,sk1.4.*,sk-only:true)	1m 5s
(ubuntu-latest,Py3.11,sk1.5.*,sk-only:true)	54s
(ubuntu-latest,Py3.10,sk1.3.*,sk-only:true)	1m 3s
(ubuntu-latest,Py3.10,sk1.5.*,sk-only:true)	57s
(ubuntu-latest,Py3.12,sk1.3.*,sk-only:true)	1m 2s
(ubuntu-latest,Py3.11,sk1.4.*,sk-only:true)	57s
(ubuntu-latest,Py3.11,sk1.6.*,sk-only:true)	1m 2s
(ubuntu-latest,Py3.12,sk1.4.*,sk-only:true)	1m 8s
(windows-latest,Py3.12,sk1.5.*,sk-only:false)	7m 19s
(ubuntu-latest,Py3.13,sk1.7.*,sk-only:true)	1m 2s
(ubuntu-latest,Py3.14,sk1.7.*,sk-only:false)	2m 50s
(ubuntu-latest,Py3.12,sk1.5.*,sk-only:false)	6m 41s
(ubuntu-latest,Py3.12,sk1.6.*,sk-only:true)	1m 1s
(ubuntu-latest,Py3.13,sk1.6.*,sk-only:true)	1m 4s
(ubuntu-latest,Py3.14,sk1.5.*,sk-only:true)	4m 16s
(ubuntu-latest,Py3.14,sk1.7.*,sk-only:true)	1m 11s
(ubuntu-latest,Py3.14,sk1.6.*,sk-only:true)	4m 24s
(ubuntu-latest,Py3.13,sk1.5.*,sk-only:true)	1m 5s
(ubuntu-latest,Py3.12,sk1.7.*,sk-only:true)	1m 3s
(ubuntu-latest,Py3.12,sk1.5.*,sk-only:true)	1m 8s
(ubuntu-latest,Py3.11,sk1.7.*,sk-only:true)	51s
	44m 52s

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