Bump ko-build/setup-ko from 0.7 to 0.8 #3777

Job	Run time
unit	3m 35s
test-docker-build (base)	36s
integration (v1.29.8, v0.56.8)	27m 49s
test-docker-build (git)	1m 8s
integration (v1.29.8, v0.65.1)	26m 56s
test-docker-build (image-processing)	46s
integration (v1.31.0, v0.56.8)	28m 31s
test-docker-build (waiter)	34s
integration (v1.31.0, v0.65.1)	28m 0s
e2e (v1.29.8, v0.56.8)	35m 12s
e2e (v1.29.8, v0.65.1)	36m 38s
e2e (v1.31.0, v0.56.8)	33m 16s
e2e (v1.31.0, v0.65.1)	37m 2s
	4h 20m 3s

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