You can cancel a friend request by following the steps below.

For mobile:

1. In the left menu, press All Groups
2. Along the bottom bar (Home, My Calendar, etc), click My Contacts
3. Scroll down to the person whose friend request you want to cancel. Press their name.
4. In their profile box, press the Pending Invite button on the left
5. Click the Retract Friend Request button
6. You have successfully canceled a friend request!

For desktop:

1. In the left menu, click on All Groups
2. Along the top bar (Home, My Calendar, etc), click My Contacts
3. Scroll down to the person whose friend request you want to cancel. Click on their name
4. On their profile box, click the Pending Invite button on the left
5. Click the Retract Friend Request button
6. You have successfully canceled a friend request!