Add executorch-et-log-disabled constraint honored by log.bzl (#20187) #711

Job	Run time
test-webgpu / test-backend-linux (webgpu, operators) / linux-job	38m 5s
test-webgpu / test-backend-linux (webgpu, models) / linux-job	16m 58s
test-webgpu / test-backend-macos	0s
test-webgpu / package-golden-artifacts	1m 31s
	56m 34s

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