az ad app credential reset documentation is out of date

The parameters listed for az ad app credential reset are out of date:

display-name should be replaced with credential-description

Example:

```
az ad app credential reset --id 00000000-0000-0000-0000-000000000000 --append --credential-description "Description" --cert "MIICoT..."
```
---
#### Document Details

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* ID: 364ccdfb-268e-08f0-a357-94a19c5213fd
* Version Independent ID: d2c1a19f-bfbd-b273-77e2-9fdb596181b5
* Content: [az ad app credential](https://learn.microsoft.com/en-us/cli/azure/ad/app/credential?view=azure-cli-latest#az-ad-app-credential-reset)
* Content Source: [latest/docs-ref-autogen/ad/app/credential.yml](https://github.com/MicrosoftDocs/azure-docs-cli/blob/main/latest/docs-ref-autogen/ad/app/credential.yml)
* Service: **active-directory**
* GitHub Login: @rloutlaw
* Microsoft Alias: **routlaw**