Correct variable name in smallest sub array with given sum problem no: 1.2

[bugudiramu]

File: https://github.com/dipjul/Grokking-the-Coding-Interview-Patterns-for-Coding-Questions/blame/master/1.-pattern-sliding-window/1.2-smallest-subarray-with-a-given-sum-easy.md#L61

In line no: 61 it should be

minLen = Math.min(minLen, windowSize - windowStart + 1);

instead of

minLen = Math.min(minLen, windowEnd - windowStart + 1);