docs: add document equations for `se_atten_v2` #7908

Job	Run time
Test Python (1, 3.8)	10m 58s
Test Python (1, 3.11)	10m 50s
Test Python (2, 3.8)	9m 36s
Test Python (2, 3.11)	9m 31s
Test Python (3, 3.8)	10m 5s
Test Python (3, 3.11)	9m 17s
Test Python (4, 3.8)	10m 9s
Test Python (4, 3.11)	9m 8s
Test Python (5, 3.8)	10m 5s
Test Python (5, 3.11)	9m 59s
Test Python (6, 3.8)	10m 35s
Test Python (6, 3.11)	9m 27s
Combine and update integration test durations (3.8)	5s
Combine and update integration test durations (3.11)	7s
Pass testing Python	2s
	1h 59m 54s

Provide feedback