window: Don’t mix and match enum types
Using NautilusNewTabPosition as NautilusWindowOpenFlags can result in a failed assertion when the value is equal to 1 (NAUTILUS_WINDOW_OPEN_FLAG_NEW_WINDOW/NAUTILUS_NEW_TAB_POSITION_END). Additionally, nautilus_window_open_location_full() checks the new tab position, so it is simply pointless to do that beforehand.
Fixes #953 (closed)