build: Lock GitHub runners' OS #3646

Job	Run time
all-runtimes	0s
lint (3.9)	48s
generate (3.9, dataplane)	31s
lint (3.10)	48s
mlserver (ubuntu-22.04, 3.9, true)	4m 9s
generate (3.9, model-repository)	30s
mlserver (ubuntu-22.04, 3.10, true)	4m 8s
generate (3.10, dataplane)	33s
runtimes (ubuntu-22.04, 3.9, sklearn, true)	2m 2s
generate (3.10, model-repository)	29s
runtimes (ubuntu-22.04, 3.9, xgboost, true)	2m 51s
runtimes (ubuntu-22.04, 3.9, lightgbm, true)	2m 8s
runtimes (ubuntu-22.04, 3.9, mlflow, true)	6m 23s
runtimes (ubuntu-22.04, 3.9, huggingface, true)	5m 41s
runtimes (ubuntu-22.04, 3.9, alibi-explain, true)	5m 39s
runtimes (ubuntu-22.04, 3.9, alibi-detect, true)	4m 34s
runtimes (ubuntu-22.04, 3.9, catboost, true)	2m 16s
runtimes (ubuntu-22.04, 3.10, sklearn, true)	1m 55s
runtimes (ubuntu-22.04, 3.10, xgboost, true)	3m 23s
runtimes (ubuntu-22.04, 3.10, lightgbm, true)	1m 59s
runtimes (ubuntu-22.04, 3.10, mlflow, true)	4m 9s
runtimes (ubuntu-22.04, 3.10, huggingface, true)	6m 20s
runtimes (ubuntu-22.04, 3.10, alibi-explain, true)	4m 11s
runtimes (ubuntu-22.04, 3.10, alibi-detect, true)	3m 44s
runtimes (ubuntu-22.04, 3.10, catboost, true)	2m 20s
	1h 11m 31s

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