Chore(doc): merge multitask training doc #1360

Job	Run time
Test Python (1, 3.9)	31m 21s
Test Python (1, 3.12)	46m 14s
Test Python (2, 3.9)	33m 46s
Test Python (2, 3.12)	40m 18s
Test Python (3, 3.9)	33m 3s
Test Python (3, 3.12)	42m 32s
Test Python (4, 3.9)	31m 44s
Test Python (4, 3.12)	38m 48s
Test Python (5, 3.9)	30m 24s
Test Python (5, 3.12)	39m 14s
Test Python (6, 3.9)	31m 16s
Test Python (6, 3.12)	39m 25s
Combine and update integration test durations (3.9)	7s
Combine and update integration test durations (3.12)	7s
Pass testing Python	3s
	7h 18m 22s

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