There are a couple of different ways to remove a favourite team.
You can do it by searching for the team and then clicking on the star to unfollow them.
You can us the calendar to find a match that the team are playing, press the three dots next to the match and then press 'Unfollow'.
In the Calendar press edit, which can be found in the top right hand corner, and then press the cross next to the teams name.
Here is a video showing each method: