revert(ci): restore backend.yml to master state #6

Job	Run time
detect what files changed	12s
cli test	2m 13s
backend migration tests	13m 30s
api docs test	6m 0s
monolith-dbs test	7m 20s
check migration	1m 16s
backend typing	4m 22s
requirements check	0s
calculate test shards	4s
api url typescript generation	0s
prepare selective tests	0s
backend test (0)	12m 52s
backend test (1)	12m 22s
backend test (11)	11m 57s
backend test (8)	12m 29s
backend test (9)	13m 31s
backend test (5)	12m 3s
backend test (12)	12m 47s
backend test (2)	12m 24s
backend test (3)	12m 1s
backend test (4)	10m 38s
backend test (10)	11m 16s
backend test (13)	12m 25s
backend test (15)	11m 18s
backend test (18)	12m 9s
backend test (21)	11m 58s
backend test (19)	10m 9s
backend test (20)	10m 56s
backend test (16)	11m 37s
backend test (17)	12m 45s
backend test (14)	11m 36s
backend test (7)	12m 21s
backend test (6)	12m 13s
Backend	3s
	4h 58m 47s

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