[REFACTOR] clean code: variable naming

Author: Gonzalo Diaz

src/hackerrank/interview_preparation_kit/trees/tree_height_of_a_binary_tree_test.py

@@ -38,8 +38,8 @@ def test_height(self):
 
             tree: BinarySearchTree = BinarySearchTree()
 
-            for x in _tt['nodes']:
-                tree.create(x)
+            for nodes in _tt['nodes']:
+                tree.create(nodes)
 
             self.assertEqual(
                 height(tree.root), _tt['answer'],
@@ -52,8 +52,8 @@ def test_height_border_case(self):
 
             tree: BinarySearchTree = BinarySearchTree()
 
-            for x in _tt['nodes']:
-                tree.create(x)
+            for nodes in _tt['nodes']:
+                tree.create(nodes)
 
             self.assertEqual(
                 height(tree.root), _tt['answer'],