Update 0021-merge-two-sorted-lists.rs

[Vishalkulkarni45]

1)code without using recursion and with recursion for merge-two-sorted-list .All the test cases passed. Both the code are present in the same file one below another bottom one is without recursion (which was not present in the earlier one)

2)provided solution for 0019-remove-nth-node-from-end-of-the-list.rs which was not present earlier

• File(s) Modified: 0021-merge-two-sorted-list.rs
• Language(s) Used: rust
• Submission URL: https://leetcode.com/problems/merge-two-sorted-lists/submissions/922409088/ File(s) Modified: 0019-remove-nth-node-from-end-of-the-list.rs
• Language(s) Used: rust
• Submission URL: https://leetcode.com/problems/remove-nth-node-from-end-of-list/submissions/924077371/

Important

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