MainWindow: Vertically center SearchBox TextPresenter (#4223)

Ryujinx.Ava/UI/Windows/MainWindow.axaml

@@ -343,6 +343,7 @@
                             Margin="5,0,5,0"
                             HorizontalAlignment="Right"
                             VerticalAlignment="Center"
+                            VerticalContentAlignment="Center"
                             DockPanel.Dock="Right"
                             KeyUp="SearchBox_OnKeyUp"
                             Text="{Binding SearchText}"