fix(calculator): correct add method

Author: mustafiz-07

src/main/java/com/thealgorithms/calculator.java

@@ -3,7 +3,7 @@
 public class calculator {
      public int add(int a, int b) {
     System.out.println("Adding numbers");
-    return a + b;  // different change
+    return a + b+1;  // different change
 }