Fix otlp-gateway readme typo #599

Job	Run time
List tests	4s
Integration Test (annotation-autodiscovery)	3m 8s
Integration Test (auth)	3m 50s
Integration Test (auto-instrumentation)	2m 21s
Integration Test (cluster-monitoring)	3m 7s
Integration Test (control-plane-monitoring)	3m 43s
Integration Test (integration-cert-manager)	2m 9s
Integration Test (integration-grafana)	3m 41s
Integration Test (integration-loki)	3m 43s
Integration Test (integration-mysql)	3m 30s
Integration Test (profiling)	2m 11s
Integration Test (prometheus-io-annotations)	2m 22s
Integration Test (sharded-kube-state-metrics)	3m 23s
Integration Test (statsd)	2m 7s
	39m 19s

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