Removed redundant/unused IWebBrowser from MainWindow.Xaml.cs
Removed redundant/unused IWebBrowser from MainWindow.Xaml.cs

MainWindow.xaml uses the MainView View/ViewModel, which contains its own IWebBrowser. Removed redundant/unused IWebBrowser from MainWindow.xaml.cs.
Briaker/CefSharp.MinimalExample,robinwassen/CefSharp.MinimalExample.Issue.1277,SergeyAvd/MinExample2,KarlWenzel/CefSharp.MinimalExample,cefsharp/CefSharp.MinimalExample,modulexcite/CefSharp.MinimalExample,SergeyAvd/MinExample2