Update app-governance-trial-user-guide.md

[WendyLiuC]

@batamig #sign_off

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

[learn-build-service-prod[bot]]

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[batamig]

Pulled into https://github.com/MicrosoftDocs/CloudAppSecurityDocs-pr/pull/3591

[batamig]

@WendyLiuC - in the main PR, I'd moved this note to the prerequisites, please look for it there when you review instead. I also removed reference to the "trial" as per @AndrewVahidnia

[ShannonLeavitt]

label:"aq-pr-triaged"