Tests

[MNT] Remove redundant `init`s in `OpenMLTask` descendants by adding ClassVar #2067

Job	Run time
(windows-latest, Py, sk0.24.*, sk-only:false)	3s
docker	3s
(ubuntu-latest, Py3.8, sk0.23.1, sk-only:false)	2s
(ubuntu-latest,Py3.11,sk1.3.*,sk-only:true)	1m 2s
(ubuntu-latest,Py3.10,sk1.7.*,sk-only:true)	1m 0s
(ubuntu-latest,Py3.10,sk1.3.*,sk-only:true)	56s
(ubuntu-latest,Py3.10,sk1.6.*,sk-only:true)	55s
(ubuntu-latest,Py3.10,sk1.4.*,sk-only:true)	59s
(ubuntu-latest,Py3.10,sk1.5.*,sk-only:true)	1m 1s
(ubuntu-latest,Py3.12,sk1.3.*,sk-only:true)	1m 1s
(ubuntu-latest,Py3.11,sk1.6.*,sk-only:true)	53s
(ubuntu-latest,Py3.13,sk1.6.*,sk-only:true)	1m 6s
(ubuntu-latest,Py3.11,sk1.5.*,sk-only:true)	56s
(ubuntu-latest,Py3.12,sk1.7.*,sk-only:true)	1m 6s
(ubuntu-latest,Py3.12,sk1.4.*,sk-only:true)	1m 9s
(ubuntu-latest,Py3.11,sk1.7.*,sk-only:true)	1m 2s
(ubuntu-latest,Py3.13,sk1.5.*,sk-only:true)	1m 12s
(ubuntu-latest,Py3.12,sk1.6.*,sk-only:true)	1m 10s
(windows-latest,Py3.12,sk1.5.*,sk-only:false)	1h 10m 46s
(ubuntu-latest,Py3.13,sk1.7.*,sk-only:true)	1m 8s
(ubuntu-latest,Py3.11,sk1.4.*,sk-only:true)	1m 2s
(ubuntu-latest,Py3.12,sk1.5.*,sk-only:true)	1m 8s
(ubuntu-latest,Py3.12,sk1.5.,pd:2.,sk-only:false)	58m 43s
(ubuntu-latest,Py3.14,sk1.5.*,sk-only:true)	4m 21s
(ubuntu-latest,Py3.14,sk1.7.*,sk-only:true)	1m 9s
(ubuntu-latest,Py3.12,sk1.5.*,sk-only:false)	1h 54m 2s
(ubuntu-latest,Py3.14,sk1.7.*,sk-only:false)	3m 29s
(ubuntu-latest,Py3.14,sk1.6.*,sk-only:true)	4m 18s
	4h 35m 42s

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