Power Apps: Modern, refreshed look for the mail app

<p>Extends the Fluent-based modern, refreshed look for model-driven apps to the mail app, providing consistent controls, spacing, colors, and visual treatment when users work in that app. This was previously enabled for the monthly channel with the 2602.1 release and is now being enabled for the semiannual channel with the 2609.3 release.</p> <p>Availability</p> <table> <thead> <tr> <th>Field</th> <th>Value</th> </tr> </thead> <tbody> <tr> <td>Applies to</td> <td>Model-driven apps</td> </tr> <tr> <td>Release channel</td> <td>Semiannual</td> </tr> <tr> <td>Version</td> <td>2609.3</td> </tr> <tr> <td>Feature scope</td> <td>Users (always enabled)</td> </tr> </tbody> </table>