feat: update 021

Author: Blankj

note/021/README.md

@@ -2,14 +2,7 @@
 
 ## Description
 
-Given a sorted array, remove the duplicates in place such that each element appear only *once* and return the new length.
-
-Do not allocate extra space for another array, you must do this in place with constant memory.
-
-For example,
-Given input array *nums* = `[1,1,2]`,
-
-Your function should return length = `2`, with the first two elements of *nums* being `1` and `2` respectively. It doesn't matter what you leave beyond the new length.
+Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
 
 **Tags:** Linked List