Clarify system key usage for MCP extension endpoints

[PaoloPia]

Updated the description of the system key requirement for MCP extension endpoints to include the 'code' querystring parameter.

[prmerger-automator]

@PaoloPia : 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 43f8d22:

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[Copilot]

Pull Request Overview

Updates documentation to clarify that the MCP extension system key can be provided via either HTTP header or querystring parameter. This clarifies the authentication options available for accessing MCP extension endpoints in Azure Functions.

• Clarified system key authentication methods for MCP extension endpoints

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[v-dirichards]

@ggailey777

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

[learn-build-service-prod]

Learn Build status updates of commit 36120f4:

✅ Validation status: passed

File	Status	Preview URL	Details
articles/azure-functions/functions-bindings-mcp.md	✅Succeeded

For more details, please refer to the build report.