Replace invalid image URL for test batch API (#2344)

Author: RobertLucian

test/apis/batch/image-classifier-alexnet/sample.json

@@ -1,6 +1,6 @@
 [
     "https://i.imgur.com/PzXprwl.jpg",
-    "https://i.imgur.com/E4cOSLw.jpg",
+    "https://i.imgur.com/a5djbnv.jpeg",
     "https://i.imgur.com/jDimNTZ.jpg",
     "https://i.imgur.com/WqeovVj.jpg"
 ]