Did you create a Space and changed your mind later? No problem: as the owner of a Space, you'll be able to delete it whenever you want.
Here's how to do it:
Tap on the three-dots symbol in the top right corner of the screen within the Space you'd like to delete.
A pop-up window with different options will appear. Tap on "Delete".
Please note: if you've been invited to a Space, you won't be able to delete it, but you can leave it whenever you want.