Update invert-a-binary-tree.md

Author: neetcode-gh

articles/invert-a-binary-tree.md

@@ -1370,21 +1370,6 @@ impl Solution {
 
 Forgetting to check for a null root causes null pointer exceptions. Always return null immediately if the root is null.
 
-### Swapping After Recursive Calls
-
-If you swap children after making recursive calls, you end up swapping already-inverted subtrees back. The swap must happen before or the recursion will undo the inversion.
-
-```python
-# Wrong: swaps after recursion undoes the inversion
-self.invertTree(root.left)
-self.invertTree(root.right)
-root.left, root.right = root.right, root.left
-# Correct: swap first, then recurse
-root.left, root.right = root.right, root.left
-self.invertTree(root.left)
-self.invertTree(root.right)
-```
-
 ### Using Wrong References After Swap
 
 After swapping, `root.left` now points to what was previously `root.right`. When recursing, make sure you're using the correct references for the swapped children.