Favoriting places adds them to the forefront of Maps & Navigation. However, there may be times when your favorite places just aren't your favorite anymore.
Unfavorite a Place
In your favorites list, tap and hold on the item you wish to unfavorite to bring up its Quick Actions
Select "Remove from Favorites"
That's it! You can also unfavorite a place by pressing the favorite icon next to the street address in the place's route details.