Fix Checkstyle whitespace issues in Knapsack.java

Author: Arpita01-work

src/main/java/com/thealgorithms/dynamicprogramming/Knapsack.java

@@ -23,7 +23,7 @@
  */
 public final class Knapsack {
 
-    private Knapsack() {}
+    private Knapsack() { }
 
     /**
      * Validates the input to ensure correct constraints.