Update overview of application gallery with Linked Sign-on note

[ruaden94]

Added note about Linked Sign-on gallery applications having a greyed out 'Create' button.

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[Copilot]

Pull request overview

This PR adds documentation clarifying the behavior of Linked Sign-on gallery applications in the Microsoft Entra ID application gallery. The change informs users that applications configured with Linked Sign-on will display a disabled 'Create' button, and explains that the Linked Sign-on URL should instead be used with the "create your own application" option.

• Added a note block explaining the greyed out 'Create' button behavior for Linked Sign-on applications

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[Copilot]

Use 'grayed' instead of 'greyed' for consistency with American English spelling conventions in Microsoft documentation.

Suggested change

	> Linked Sign-on gallery applications will have a greyed out 'Create' button. The Linked Sign-on URL is provided to be used in the create your own application option.
	> Linked Sign-on gallery applications will have a grayed out 'Create' button. The Linked Sign-on URL is provided to be used in the create your own application option.

[ttorble]

@omondiatieno

Can you review the proposed changes?

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