`az role assignment delete` returns an error if the role assignment does not exist

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**Describe the bug**
The `az role assignment delete --assignee {object id} --role {role} --subscription {sub id}` command returns an error if the assigment does not exist. The message is `ERROR: No matched assignments were found to delete`.

This is inconsistent with the behavior of `az role assignment create`, which does **not** return an error if the role assignment already exists.

We are trying to use the delete command in some automated workflows, and the behavior of delete imposes difficulties. To make things work we are having to query the assignments first. That requires extra permissions that would otherwise not be needed.

**Expected behavior**
The delete command should be idempotent. It should not fail if the item being deleted does not exist.

**Environment summary**
GitHub Actions workflow, Ubuntu, AZ CLI 2.27