Given a binary tree root and an integer target, delete all the leaf nodes with value target.
Note that once you delete a leaf node with value target, if its parent node becomes a leaf node and has the value target, it should also be deleted (you need to continue doing that until you cannot).
[1, 3000]1 <= Node.val, target <= 1000root = [1,2,3,2,null,2,4], target = 2[1,null,3,null,4]root = [1,3,3,3,2], target = 3[1,3,null,null,2]root = [1,2,null,2,null,2], target = 2[1]