Fixes duplicate namespace declerations

[beeradmoore]

There are a few places where getting started guides list the sample as

<ContentPage   
    xmlns:syncfusion=xmlns:syncfusion="clr-namespace:Syncfusion.Maui.Toolkit.Expander;assembly=Syncfusion.Maui.Toolkit">

but xmlns:syncfusion=xmlns:syncfusion=" is incorrect.

I checked for other instances of =xmlns but could not find any so I assume these six places are the only places with the issue.

[SyncfusionBuild]

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