Bump go.opentelemetry.io/otel/trace from 1.19.0 to 1.21.0 in /extension/zpagesextension #820

Job	Run time
govulncheck	1m 18s
setup-environment	34s
lint	1m 30s
test-coverage	1m 26s
checks	27s
cross-build-collector (darwin, amd64)	12s
unittest-matrix (~1.21.3)	1m 19s
unittest-matrix (~1.20.10)	1m 18s
cross-build-collector (darwin, arm64)	7s
cross-build-collector (linux, 386)	8s
cross-build-collector (linux, amd64)	12s
cross-build-collector (linux, arm64)	11s
cross-build-collector (linux, ppc64le)	9s
cross-build-collector (linux, arm, 7)	9s
cross-build-collector (linux, s390x)	7s
cross-build-collector (windows, 386)	8s
cross-build-collector (windows, amd64)	7s
unittest	1s
	9m 23s

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