removed the reused code and did the fix

[Bhavyaatrivedi]

• File(s) Modified: 0021-merge-two-sorted-lists.cpp
• Language(s) Used:cpp
• Submission URL: https://leetcode.com/problems/[problem-name]/submissions/xxxxxxxxx/

Important

Please make sure the file name is lowercase and a duplicate file does not already exist before merging.