Update Mouse to FrameworkElementExtensions

This will fix the oversight in the documentation after the 7.0 breaking change

Author: Panda-Sharp

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/Mouse/MouseCursorPage.bind

@@ -8,7 +8,7 @@
                 Margin="50,100,20,20"
                 HorizontalAlignment="Left"
                 VerticalAlignment="Top"
-                ui:Mouse.Cursor="UniversalNo"
+                ui:FrameworkElementExtensions.Cursor="UniversalNo"
                 Background="DeepSkyBlue">
             <TextBlock Margin="4"
                        HorizontalAlignment="Center"
@@ -40,4 +40,4 @@
                 ui:Mouse.Cursor="Hand"
                 Content="Button with Hand cursor, just like on web" />
     </Grid>
-</Page>
+</Page>