Remove 'Enter' hotkey in settings menu (#95)

This allows the Enter key to be bound to a button when using the
Avalonia UI.

src/Ryujinx/UI/Windows/SettingsWindow.axaml

@@ -109,7 +109,6 @@
             HorizontalAlignment="Right"
             ReverseOrder="{Binding IsMacOS}">
             <Button
-                HotKey="Enter"
                 Classes="accent"
                 Content="{ext:Locale SettingsButtonOk}"
                 Command="{Binding OkButton}" />