reduce space complexity from O(n) to O(1)

[NITIN23329]

O(N) solution : https://github.com/NITIN23329/LeetCode/blob/c6b42b50f0692df6ad329fbacb0c7e8dd7e191f1/Stack/ScoreOfParentheses.java#L1 problem link : https://leetcode.com/problems/score-of-parentheses/