Fixing credential scopes in code-create-chat-client-entra.md

[hugogeraldes]

The current version indicates the scope https://cognitiveservices.azure.com/ or "https://cognitiveservices.azure.com/.default" to be used for the credentials.
This is currently incorrect and causes the code to fail.
The correct scope to be used (verified with samples for Python, Javascript, C# and REST) is "https://ai.azure.com/" or "https://ai.azure.com/.default"

[prmerger-automator]

@hugogeraldes : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[learn-build-service-prod]

Learn Build status updates of commit 9bee00a:

✅ Validation status: passed

File	Status	Preview URL	Details
articles/ai-foundry/foundry-models/includes/code-create-chat-client-entra.md	✅Succeeded

For more details, please refer to the build report.

[v-regandowner]

@santiagxf - Can you review the proposed changes?

IMPORTANT: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

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[v-dirichards]

@santiagxf Could you review this proposed update to your article and enter #sign-off in a comment if it's ready to merge?

Thanks!