Clarify case sensitivity for custom security attributes

[stuart938503]

Added note about case sensitivity for custom security attribute values.

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[learn-build-service-prod]

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[Copilot]

Pull Request Overview

This PR adds clarification about case sensitivity for custom security attribute values in the workflow documentation. This helps users understand that attribute values must match exactly in terms of capitalization.

• Added a note explaining that custom security attribute values are case-sensitive

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[v-dirichards]

@OWinfreyATL

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"
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