vet: add check for trailing spaces #11850

Job	Run time
tests (vet, 1.22)	2m 34s
tests (vet, 1.22)	2m 34s
tests (extras, 1.22)	2m 39s
tests (extras, 1.22)	2m 39s
vet-proto	28s
vet-proto	28s
tests (tests, 1.22)	3m 38s
tests (tests, 1.22)	3m 55s
tests (tests, 1.22, -race)	5m 40s
tests (tests, 1.22, -race)	5m 40s
tests (tests, 1.22, -race -tags=buffer_pooling)	5m 42s
tests (tests, 1.22, -race -tags=buffer_pooling)	5m 42s
tests (tests, 1.22, 386)	4m 45s
tests (tests, 1.22, 386)	4m 45s
tests (tests, 1.22, arm64)	6m 27s
tests (tests, 1.22, arm64)	6m 27s
tests (tests, 1.21)	3m 49s
tests (tests, 1.21)	3m 49s
	1h 11m 41s

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