wayland: Don't round source geometry size

.toSize() exists from the times when surfaceSize used to be a QSize. It
shouldn't matter in practice though.

src/wayland/surface_interface.cpp

@@ -611,7 +611,7 @@ void SurfaceInterfacePrivate::applyState(SurfaceState *next)
         if (current.viewport.destinationSize.isValid()) {
             surfaceSize = current.viewport.destinationSize;
         } else if (current.viewport.sourceGeometry.isValid()) {
-            surfaceSize = current.viewport.sourceGeometry.size().toSize();
+            surfaceSize = current.viewport.sourceGeometry.size();
         } else {
             surfaceSize = implicitSurfaceSize;
         }