style: enable HideUtilityClassConstructor in checkstyle (#5147)

src/main/java/com/thealgorithms/strings/ValidParentheses.java

@@ -4,7 +4,9 @@ package com.thealgorithms.strings;
 //        the same type of brackets. Open brackets must be closed in the correct order. Every close
 //        bracket has a corresponding open bracket of the same type.
 
-public class ValidParentheses {
+public final class ValidParentheses {
+    private ValidParentheses() {
+    }
     public static boolean isValid(String s) {
         char[] stack = new char[s.length()];
         int head = 0;