Update README with new LeetCode log

Author: github-actions[bot]

README.md

@@ -3,6 +3,7 @@
 ## 解いた問題一覧
 
 <!-- log:start -->
+- 2025-07-07 14:12: [2215.find-the-difference-of-two-arrays.py](problems/python/2215.find-the-difference-of-two-arrays.py)
 - 2025-07-07 13:25: [1732.find-the-highest-altitude.py](problems/python/1732.find-the-highest-altitude.py)
 - 2025-07-07 13:25: [643.maximum-average-subarray-i.py](problems/python/643.maximum-average-subarray-i.py)
 - 2025-07-07 12:51: [724.find-pivot-index.py](problems/python/724.find-pivot-index.py)