Update 0217-contains-duplicate.go

[mbn96]

Removing the else clause. Looks more concise

• File(s) Modified: 0001-two-sum.py, 0002-add-two-numbers.py, etc...
• Language(s) Used: python, javascript, etc...
• 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.

[hiendevt]

Suggested change

	nums_map := map[int]bool{}
	nums_map := map[int]struct{}{}

It may make sense to use the struct{} type here because it doesn’t occupy any memory as opposed to bool.