update explanation square using ^

Author: anonimak

LeetcodeProblems/Algorithms/Happy_Number.js

@@ -16,10 +16,10 @@ Example 1:
 Input: n = 19
 Output: true
 Explanation:
-12 + 92 = 82
-82 + 22 = 68
-62 + 82 = 100
-12 + 02 + 02 = 1
+1^2 + 9^2 = 82
+8^2 + 2^2 = 68
+6^2 + 8^2 = 100
+1^2 + 0^2 + 0^2 = 1
 
 Example 2:
 Input: n = 2
@@ -46,4 +46,4 @@ function checkHappyNumber(n){
     return checkHappyNumber(digit)
 }
 
-module.exports.isHappy = isHappy;
+module.exports.isHappy = isHappy;