style(pmd): fix EmptyControlStatement in validate() by returning early when src==dst

Author: SamXop123

src/main/java/com/thealgorithms/graph/YensKShortestPaths.java

@@ -133,6 +133,7 @@ private static void validate(int[][] weights, int src, int dst, int k) {
         }
         if (src == dst) {
             // allowed: path is [src] with cost 0 (handled by dijkstra)
+            return;
         }
     }