BuddyPress.org

You could always use this snippet and maybe adjust the height of the field/container if needed:

.buddyx-mem-cover-img {
visibility: hidden;
}

Hello

You might already have solved this, since the post is 2 months old – however – I just wanted to mention that this can be done with a simple setting.

Go to Settings > Forums > Forum Integration for BuddyPress

Change the setting in the box “Allow BuddyPress Groups to have their own forums”.

Hope it helps. 🙂