Update osdu-azure/dataset/values.yaml

. Issue: Getting dataset GLAB 500 error code as an environment variable not set

https://osdu-glab.msft-osdu-test.org/api/dataset/v1/retrievalInstructions

. Fix: Updating the external_dataset_service_endpoint name and its associated value

. Pipeline passed after update: https://community.opengroup.org/osdu/platform/deployment-and-operations/helm-charts-azure/-/pipelines/164285