Update preprocessor_config.json

preprocessor_config.json

@@ -18,9 +18,10 @@
     "height": 16,
     "width": 16
   },
+  "processor_class": "PixtralProcessor",
   "resample": 3,
   "rescale_factor": 0.00392156862745098,
   "size": {
-    "longest_edge": 1024
+    "longest_edge": 256
   }
-}
+}