More detail around non-required arguments for create

In creating an Azure pipeline certain arguments if not specified explicitly will make an attempt to auto detect based on the repository given. It would be better if in the documentation this was more explicit in saying that this attempt will be made but if the attempt fails for any reason this becomes a required argument. This would make required arguments for creation much clearer.

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#### Document Details

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* ID: 2a2123ca-5408-8f93-6f5c-93fe74684523
* Version Independent ID: 7a03fe73-da7f-9b5a-38e7-ef51d85d49fd
* Content: [az pipelines](https://docs.microsoft.com/en-us/cli/azure/ext/azure-devops/pipelines?view=azure-cli-latest#ext-azure-devops-az-pipelines-create)
* Content Source: [latest/docs-ref-autogen/ext/azure-devops/pipelines.yml](https://github.com/MicrosoftDocs/azure-docs-cli/blob/live/latest/docs-ref-autogen/ext/azure-devops/pipelines.yml)
* GitHub Login: @rloutlaw
* Microsoft Alias: **routlaw**

Start with latest/docs-ref-autogen/ext/azure-devops/pipelines.yml and the az pipelines create documentation linked in the issue. Check the argument descriptions and make the auto-detection attempt and its fallback to required status explicit, then verify the generated documentation clearly explains which arguments are required when detection fails.

Written by the indexing model from the issue text.