Update module golang.org/x/net to v0.20.0 #16614

Job	Run time
govulncheck	58s
setup-environment	29s
lint	3m 10s
unittest-matrix (~1.21.5)	5m 2s
unittest-matrix (~1.20.12)	4m 12s
checks	1m 57s
test-coverage	4m 31s
cross-build-collector (darwin, amd64)	35s
cross-build-collector (darwin, arm64)	35s
cross-build-collector (linux, 386)	36s
cross-build-collector (linux, amd64)	40s
cross-build-collector (linux, arm64)	35s
cross-build-collector (linux, ppc64le)	44s
cross-build-collector (linux, arm, 7)	36s
cross-build-collector (linux, s390x)	39s
cross-build-collector (windows, 386)	40s
cross-build-collector (windows, amd64)	41s
unittest	1s
	26m 41s

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