Error in code sample

The code sample provided for creating a key vault certificate is incorrect. It throws an exception. The problem and solution are discussed on this post on stack overflow. https://stackoverflow.com/questions/67840500/error-creating-key-vault-certificate-in-azure-cli

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#### Document Details

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* ID: a9c661d7-bf43-5354-015e-3859f30a42a2
* Version Independent ID: fa69e552-5904-ce97-d02c-915c819bdde1
* Content: [az keyvault certificate](https://docs.microsoft.com/en-us/cli/azure/keyvault/certificate?view=azure-cli-latest)
* Content Source: [latest/docs-ref-autogen/keyvault/certificate.yml](https://github.com/MicrosoftDocs/azure-docs-cli/blob/master/latest/docs-ref-autogen/keyvault/certificate.yml)
* Service: **key-vault**
* GitHub Login: @rloutlaw
* Microsoft Alias: **routlaw**