Show examples of cancellation in LRO docs

In or related to https://azure.github.io/typespec-azure/docs/getstarted/azure-core/step06, could you show an example of how services can cancel an LRO? The REST API Stewardship Board has guidelines - or at least recommendations - on this: https://github.com/microsoft/api-guidelines/blob/vNext/azure/ConsiderationsForServiceDesign.md#controlling-a-long-running-operation

Start with the Step 06 LRO documentation page linked in the issue, then read the REST API Stewardship Board's “Controlling a long-running operation” guidance. Add a service-side cancellation example that follows those recommendations and verify that the page clearly explains the expected behavior.

Written by the indexing model from the issue text.