Reference "permission add" from "permission grant"

Please make it clear under the "permission grant" reference that it's required to first call "permission add". I didn't know that and spent a while debugging an error with calling grant first.

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#### Document Details

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* ID: 6a5b5348-f67e-ef14-0529-4c80fddd4bc6
* Version Independent ID: bfd7e6b1-1fba-3d25-8ee3-5105bcf4157d
* Content: [az ad app permission](https://learn.microsoft.com/en-us/cli/azure/ad/app/permission?view=azure-cli-latest)
* Content Source: [latest/docs-ref-autogen/ad/app/permission.yml](https://github.com/MicrosoftDocs/azure-docs-cli/blob/main/latest/docs-ref-autogen/ad/app/permission.yml)
* Service: **active-directory**
* GitHub Login: @rloutlaw
* Microsoft Alias: **routlaw**