Tests

[MNT] Remove redundant `init`s in `OpenMLTask` descendants by adding ClassVar #2295

Job	Run time
(windows-latest, Py, sk0.24.*, sk-only:false)	4s
docker	2s
(ubuntu-latest, Py3.8, sk0.23.1, sk-only:false)	2s
(ubuntu-latest,Py3.10,sk1.7.*,sk-only:true)	10m 59s
(ubuntu-latest,Py3.10,sk1.5.*,sk-only:true)	57s
(ubuntu-latest,Py3.10,sk1.6.*,sk-only:true)	1m 8s
(ubuntu-latest,Py3.10,sk1.3.*,sk-only:true)	3m 9s
(ubuntu-latest,Py3.11,sk1.3.*,sk-only:true)	1m 0s
(ubuntu-latest,Py3.14,sk1.7.*,sk-only:true)	6m 3s
(ubuntu-latest,Py3.11,sk1.5.*,sk-only:true)	4m 57s
(ubuntu-latest,Py3.14,sk1.7.*,sk-only:false)	1h 12m 52s
(ubuntu-latest,Py3.12,sk1.5.*,sk-only:true)	3m 9s
(ubuntu-latest,Py3.14,sk1.6.*,sk-only:true)	6m 9s
(ubuntu-latest,Py3.12,sk1.4.*,sk-only:true)	4m 20s
(ubuntu-latest,Py3.12,sk1.6.*,sk-only:true)	1m 1s
(ubuntu-latest,Py3.10,sk1.4.*,sk-only:true)	59s
(ubuntu-latest,Py3.12,sk1.7.*,sk-only:true)	4m 1s
(ubuntu-latest,Py3.12,sk1.5.,pd:2.,sk-only:false)	6m 35s
(ubuntu-latest,Py3.13,sk1.5.*,sk-only:true)	3m 59s
(ubuntu-latest,Py3.13,sk1.7.*,sk-only:true)	1m 20s
(windows-latest,Py3.12,sk1.5.*,sk-only:false)	1h 30m 43s
(ubuntu-latest,Py3.12,sk1.5.*,sk-only:false)	1h 19m 20s
(ubuntu-latest,Py3.11,sk1.7.*,sk-only:true)	1m 4s
(ubuntu-latest,Py3.13,sk1.6.*,sk-only:true)	2m 26s
(ubuntu-latest,Py3.12,sk1.3.*,sk-only:true)	17m 6s
(ubuntu-latest,Py3.14,sk1.5.*,sk-only:true)	4m 26s
(ubuntu-latest,Py3.11,sk1.4.*,sk-only:true)	1m 0s
(ubuntu-latest,Py3.11,sk1.6.*,sk-only:true)	6m 6s
	5h 34m 57s

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