Add details to `az monitor app-insights api-key create`

The documentation for `az monitor app-insights api-key create` includes the following:

> `--read-properties`
> A space seperated list of names of read Roles for this API key to inherit.
>
> `--write-properties`
> A space seperated list of names of write Roles for this API key to inherit.

It should include the actual Role names that are valid (`ReadTelemetry`, `AuthenticateSDKControlChannel`; `WriteAnnotations`).

This information is in the script documentation at https://github.com/azure/azure-cli-extensions/blob/86680f7a592c659456feb605104809efa5fae353/src/application-insights/azext_applicationinsights/_help.py#L179-L184 but I shouldn't need to go look up the source code to find it out.

Additionally, there is a typo in "separated" that has been fixed in https://github.com/Azure/azure-cli-extensions/pull/3957.

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* ID: 16480120-f1e7-5319-2e66-316f0e907222
* Version Independent ID: b8f61f0c-f3af-fbc4-3ac5-02b9d6063c26
* Content: [az monitor app-insights api-key](https://docs.microsoft.com/en-us/cli/azure/monitor/app-insights/api-key?view=azure-cli-latest#az_monitor_app_insights_api_key_create-optional-parameters)
* Content Source: [latest/docs-ref-autogen/monitor/app-insights/api-key.yml](https://github.com/MicrosoftDocs/azure-docs-cli/blob/master/latest/docs-ref-autogen/monitor/app-insights/api-key.yml)
* Service: **monitoring-and-diagnostics**
* GitHub Login: @rloutlaw
* Microsoft Alias: **routlaw**