video_core: Bump OpenGL version to 4.3 on desktop

* The current backend heavily depends on many extensions for shadow
  rendering and texture cubes in the fragment shaders. All these
  extensions were incorporated to core in 4.3. Support is practically
  ubiquitous and requiring support for it makes things a lot easier

src/citra_qt/main.cpp

@@ -2441,7 +2441,7 @@ int main(int argc, char* argv[]) {
     QCoreApplication::setApplicationName(QStringLiteral("Citra"));
 
     QSurfaceFormat format;
-    format.setVersion(3, 3);
+    format.setVersion(4, 3);
     format.setProfile(QSurfaceFormat::CoreProfile);
     format.setSwapInterval(0);
     // TODO: expose a setting for buffer value (ie default/single/double/triple)