`SampleApps\webview2_sample_uwp` references a missing file

`Properties\Default.rd.xml` is referenced by [the VS project](https://github.com/MicrosoftEdge/WebView2Samples/blob/5b3625aa547d59647a7363799d1c1b413bce078c/SampleApps/webview2_sample_uwp/WebView2_UWP.csproj#L135), but that file does not exist, so that causes an error when trying to build.