update heatmap brick padding mock to show the problem

Author: alexcjohnson

test/image/baselines/heatmap_brick_padding.png

@@ -2,25 +2,23 @@
   "data": [
     {
       "z": [
-        [
-          1,
-          20,
-          30
-        ],
-        [
-          20,
-          1,
-          60
-        ],
-        [
-          30,
-          60,
-          1
-        ]
+        [1, 2, 3, 4, 5],
+        [3, 4, 5, 6, 7],
+        [5, 6, 7, 8, 9],
+        [7, 8, 9, 8, 7],
+        [9, 8, 7, 6, 5]
       ],
-      "xgap": 9,
-      "ygap": 6,
+      "xgap": 20,
+      "ygap": 12,
+      "x0": 0.5,
+      "y0": 0.5,
       "type": "heatmap"
     }
-  ]
+  ],
+  "layout": {
+    "width": 400,
+    "height": 400,
+    "xaxis": {"zeroline": false, "showline": true, "mirror": true, "dtick": 1},
+    "yaxis": {"zeroline": false, "showline": true, "mirror": true, "dtick": 1}
+  }
 }