Fix a bug in A_Star.Graph in jdk17 (#2842)

Co-authored-by: Andrii Siriak <siryaka@gmail.com>

src/main/java/com/thealgorithms/datastructures/graphs/A_Star.java

@@ -16,7 +16,7 @@ public class A_Star {
         public Graph(int size) {
             this.graph = new ArrayList<>();
             for (int i = 0; i < size; i++) {
-                this.graph.set(i, new ArrayList<>());
+                this.graph.add(new ArrayList<>());
             }
         }