Fix outdate number error of findRepeatNumber(#281)

Author: yanglbme

lcof/面试题03. 数组中重复的数字/Solution.py

@@ -5,3 +5,5 @@ def findRepeatNumber(self, nums: List[int]) -> int:
                 if num == nums[num]:
                     return num
                 nums[i], nums[num] = nums[num], nums[i]
+                num = nums[i]
+        return -1