app: don't use hidpi application attribute

This seems to cause issues on various platforms and isn't required a lot of the
time:

* macOS doesn't need this since the HiDPI setting is in the bundle's Info.plist
* Windows doesn't need this, in fact it seems to make fractional HiDPI worse
* Linux... who knows how to get HiDPI working on Linux

app/main.cpp

@@ -50,7 +50,7 @@ int main(int argc, char *argv[]) {
   format.setProfile(QSurfaceFormat::CoreProfile);
   QSurfaceFormat::setDefaultFormat(format);
 
-  QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+  //QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
   QCoreApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
 
   // Create application instance