Correct typo in json files

resources/json_files/ex_2.json

@@ -6,5 +6,5 @@
         [2, 1, 0, 0, 0, 1]
     ],
     "constants": [5, 3, 4],
-    "objective": [2, 3, 1, 0, 0, 0]
+    "objective": [2, 4, 1, 0, 0, 0]
 }

resources/json_files/ex_3.json

@@ -6,5 +6,5 @@
         [2, 1, 0]
     ],
     "constants": [5, 3, 4],
-    "objective": [2, 3, 1]
+    "objective": [2, 4, 1]
 }