Bump go.opentelemetry.io/otel/sdk from 1.19.0 to 1.21.0 in /exporter #817

Job	Run time
govulncheck	1m 10s
setup-environment	30s
checks	24s
lint	1m 28s
test-coverage	1m 23s
unittest-matrix (~1.21.3)	1m 16s
unittest-matrix (~1.20.10)	1m 16s
cross-build-collector (darwin, amd64)	14s
cross-build-collector (darwin, arm64)	12s
cross-build-collector (linux, 386)	14s
cross-build-collector (linux, amd64)	8s
cross-build-collector (linux, arm64)	15s
cross-build-collector (linux, ppc64le)	10s
cross-build-collector (linux, arm, 7)	15s
cross-build-collector (linux, s390x)	13s
cross-build-collector (windows, 386)	11s
cross-build-collector (windows, amd64)	11s
unittest	1s
	9m 31s

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