Fix bug with dropping hifi images not working on Windows

URLs on Windows included three forward-slashes, ex `file:///C:...`.
Using `toLocalFile()` correctly stringifies the location.

interface/src/Application.cpp

@@ -1315,7 +1315,7 @@ void Application::dropEvent(QDropEvent *event) {
     const QMimeData *mimeData = event->mimeData();
     foreach (QUrl url, mimeData->urls()) {
         if (url.url().toLower().endsWith(SNAPSHOT_EXTENSION)) {
-            snapshotPath = url.url().remove("file://");
+            snapshotPath = url.toLocalFile();
             break;
         }
     }