Update distributed-tracing.md

[hdhalter]

Description

Tell us about your request. Provide a summary of the request and all versions that are affected.

1. Update the document to add the setting telemetry.feature.tracer.enabled: true which is a prerequisite to enable this feature.
2. Fix typo - typo related to the grpc configuration for traces, the class in the docs is mentioned incorrectly telemetry.otel.tracer.span.exporter.class=org.opensearch.telemetry.tracing.exporter.OtlpGrpcSpanExporterProvider, while it should have the following value telemetry.otel.tracer.span.exporter.class: io.opentelemetry.exporter.otlp.trace.OtlpGrpcSpanExporter

What other resources are available? Provide links to related issues, POCs, steps for testing, etc. https://github.com/opensearch-project/OpenSearch/issues/13323

Issues Resolved

Closes https://github.com/opensearch-project/documentation-website/issues/7028

Checklist

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