Tests

[MNT] Remove redundant `init`s in `OpenMLTask` descendants by adding ClassVar #1860

Job	Run time
(ubuntu-latest, Py3.8, sk0.23.1, sk-only:false)	2s
docker	3s
(windows-latest, Py, sk0.24.*, sk-only:false)	4s
(ubuntu-latest,Py3.10,sk1.3.*,sk-only:true)	59s
(ubuntu-latest,Py3.10,sk1.7.*,sk-only:true)	1m 0s
(ubuntu-latest,Py3.11,sk1.3.*,sk-only:true)	1m 3s
(ubuntu-latest,Py3.10,sk1.5.*,sk-only:true)	1m 3s
(ubuntu-latest,Py3.10,sk1.4.*,sk-only:true)	1m 13s
(ubuntu-latest,Py3.13,sk1.6.*,sk-only:true)	1m 4s
(ubuntu-latest,Py3.12,sk1.6.*,sk-only:true)	1m 7s
(windows-latest,Py3.12,sk1.5.*,sk-only:false)	1h 13m 12s
(ubuntu-latest,Py3.12,sk1.3.*,sk-only:true)	1m 10s
(ubuntu-latest,Py3.12,sk1.7.*,sk-only:true)	1m 11s
(ubuntu-latest,Py3.12,sk1.5.*,sk-only:false)	1h 11m 4s
(ubuntu-latest,Py3.11,sk1.6.*,sk-only:true)	55s
(ubuntu-latest,Py3.11,sk1.4.*,sk-only:true)	55s
(ubuntu-latest,Py3.11,sk1.5.*,sk-only:true)	53s
(ubuntu-latest,Py3.10,sk1.6.*,sk-only:true)	54s
(ubuntu-latest,Py3.11,sk1.7.*,sk-only:true)	1m 2s
(ubuntu-latest,Py3.12,sk1.5.*,sk-only:true)	1m 4s
(ubuntu-latest,Py3.12,sk1.4.*,sk-only:true)	1m 9s
(ubuntu-latest,Py3.14,sk1.7.*,sk-only:false)	1h 6m 4s
(ubuntu-latest,Py3.14,sk1.5.*,sk-only:true)	4m 21s
(ubuntu-latest,Py3.13,sk1.7.*,sk-only:true)	1m 6s
(ubuntu-latest,Py3.14,sk1.7.*,sk-only:true)	1m 14s
(ubuntu-latest,Py3.13,sk1.5.*,sk-only:true)	1m 6s
(ubuntu-latest,Py3.14,sk1.6.*,sk-only:true)	4m 24s
	3h 59m 22s

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