Fix jumping of SplitView pane in right aligned layout via min width (#1899)

## Description
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Fixes jumping by fixing width.
## Motivation and Context
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Fixes #1897
## How Has This Been Tested?
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## Screenshots (if appropriate):

## Types of changes
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- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)

Author: marcelwgn

WinUIGallery/Samples/ControlPages/SplitViewPage.xaml

@@ -22,12 +22,13 @@
     <StackPanel>
         <controls:ControlExample HeaderText="A basic SplitView.">
 
-            <Grid Height="300" VerticalAlignment="Top">
+            <Grid Height="300" Width="400" VerticalAlignment="Top">
                 <SplitView
                     x:Name="splitView"
                     CompactPaneLength="{x:Bind compactPaneLengthSlider.Value, Mode=OneWay}"
                     DisplayMode="CompactOverlay"
                     IsPaneOpen="{x:Bind togglePaneButton.IsChecked, Mode=TwoWay, Converter={StaticResource nullableBooleanToBooleanConverter}}"
+                    Width="400" 
                     IsTabStop="False"
                     OpenPaneLength="{x:Bind openPaneLengthSlider.Value, Mode=OneWay}"
                     PaneBackground="{ThemeResource SystemControlBackgroundChromeMediumLowBrush}">