docs(spanmetrics): Fix feature gate name in README

[liamfd]

Hello! It looks like #41865 introduced a new feature flag and associated docs. The docs list it as connector.spanmetrics.includeServiceInstanceID, but I believe it's actually connector.spanmetrics.includeCollectorInstanceID. Looks like it might've changed due to feedback in the PR

Passing connector.spanmetrics.includeServiceInstanceID resulted in the following error for me:

"Error: invalid argument "connector.spanmetrics.includeServiceInstanceID" for "--feature-gates" flag: no such feature gate "connector.spanmetrics.includeServiceInstanceID". valid gates: [awsemf.nodimrollupdefault clickhouse.json cloudfoundry.resourceAttributes.allow confighttp.framedSnappy confmap.enableMergeAppendOption connector.datadogconnector.NativeIngest connector.servicegraph.legacyLatencyMetricNames connector.servicegraph.legacyLatencyUnitMs connector.servicegraph.virtualNode connector.spanmetrics.excludeResourceMetrics connector.spanmetrics.includeCollectorInstanceID connector.spanmetrics.legacyMetricNames connector.spanmetrics.useSecondAsDefaultMetricsUnit datadog.EnableOperationAndResourceNameV2 datadog.EnableReceiveResourceSpansV2 exporter.PersistRequestContext exporter.awsxray.skiptimestampvalidation exporter.datadogexporter.DisableAPMStats exporter.datadogexporter.InferIntervalForDeltaMetrics exporter.datadogexporter.TraceExportUseCustomHTTPClient exporter.datadogexporter.UseLogsAgentExporter exporter.datadogexporter.metricexportnativeclient exporter.datadogexporter.metricexportserializerclient exporter.datadogexporter.metricremappingdisabled exporter.googlecloud.CustomMonitoredResources exporter.googlemanagedprometheus.intToDouble exporter.kafkaexporter.UseFranzGo exporter.prometheusexporter.DisableAddMetricSuffixes exporter.prometheusremotewritexporter.EnableMultipleWorkers exporter.prometheusremotewritexporter.RetryOn429 exporter.prometheusremotewritexporter.enableSendingRW2 exporter.xray.allowDot extension.jaegerremotesampling.replaceThriftWithProto extension.sumologic.updateCollectorMetadata filelog.allowFileDeletion filelog.allowHeaderMetadataParsing filelog.decompressFingerprint filelog.mtimeSortType filter.filterlog.useOTTLBridge filter.filtermetric.useOTTLBridge filter.filterspan.useOTTLBridge hostmetrics.process.bootTimeCache k8sattr.fieldExtractConfigRegex.disallow k8sattr.labelsAnnotationsSingular.allow logs.assignKeys logs.jsonParserArray metricsgeneration.MatchAttributes otelcol.printInitialConfig parser.uri.ecscompliant pdata.enableRefCounting pdata.useCustomProtoEncoding pdata.useProtoPooling pkg.translator.prometheus.NormalizeName pkg.translator.prometheus.PermissiveLabelSanitization postgresqlreceiver.preciselagmetrics processor.resourcedetection.propagateerrors processor.resourcedetection.removeGCPFaasID processor.tailsamplingprocessor.disableinvertdecisions processor.tailsamplingprocessor.metricstatcountspanssampled processor.tailsamplingprocessor.recordpolicy processor.transform.ConvertBetweenSumAndGaugeMetricContext receiver.azureeventhubreceiver.UseAzeventhubs receiver.datadogreceiver.Enable128BitTraceID receiver.hostmetricsreceiver.UseLinuxMemAvailable receiver.jaeger.DisableRemoteSampling receiver.kafkametricsreceiver.UseFranzGo receiver.kafkareceiver.UseFranzGo receiver.mongodb.removeDatabaseAttr receiver.postgresql.connectionPool receiver.postgresql.separateSchemaAttr receiver.prometheusreceiver.EnableCreatedTimestampZeroIngestion receiver.prometheusreceiver.EnableNativeHistograms receiver.prometheusreceiver.RemoveLegacyResourceAttributes receiver.prometheusreceiver.RemoveStartTimeAdjustment receiver.prometheusreceiver.UseCollectorStartTimeFallback receiver.prometheusreceiver.UseCreatedMetric receiver.sqlserver.RemoveServerResourceAttribute receiver.vcenter.resourcePoolMemoryUsageAttribute receiverhelper.newReceiverMetrics service.AllowNoPipelines service.noopTracerProvider service.profilesSupport stanza.synchronousLogEmitter telemetry.UseLocalHostAsDefaultMetricsAddress telemetry.disableHighCardinalityMetrics telemetry.newPipelineTelemetry transform.flatten.logs]"

So here I just fix the name in the docs.

Description

n/a

Link to tracking issue

n/a

Testing

I copy pasted the flag name string from the doc change into my dockerfile and made sure it ran (no typos).

Documentation

Just updating connector/spanmetricsconnector/README.md as described above.

---

Thanks for the feature!

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: codeboten / name: Alex Boten (db3eb60)
• ✅ login: liamfd / name: Liam Doran (5b2c3be)

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[github-actions]

Welcome, contributor! Thank you for your contribution to opentelemetry-collector-contrib.

Important reminders:

• Please review our Contributing Guidelines.
• Don't forget to sign the Contributor License Agreement (CLA) if you haven't already.

A maintainer will review your pull request soon. Thank you for helping make OpenTelemetry better!

[codeboten]

Thanks @liamfd!

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