Name the option "Settings" rather than "Preferences" on MacOS
@lukaso stated that "Preferences" should be called "Settings..." on MacOS per their standards, and in fact was called that before the GTK3 menu port. Since we already conditionally change the menu label for "About GIMP" vs. "About" depending on platform, this seems like an easy change.
@lukaso, please let me know if this works when you have time - thanks!