test: update mock bar_attrs_group_norm

* Updated the mock bar_attrs_group_norm so that it exercises the
  functionality to rotate bar texts.

Author: n-riesco

test/image/mocks/bar_attrs_group_norm.json

@@ -1,24 +1,24 @@
 {
     "data":[
         {
-            "text":[100,125,150,175],
+            "text":0.5,
             "textposition":"outside",
             "outsidetextfont": {"size":32},
-            "base":4,
-            "x":[3,2,1,0],
+            "base":[100,40,25,10],
+            "x":[-50,10,25,40],
             "type":"bar"
         }, {
-            "text":[100,125,150,175],
+            "text":0.5,
             "textposition":"inside",
-            "base":[7,6,5,4],
-            "x":[1,2,3,4],
+            "base":[0,60,75,90],
+            "x":[50,-10,-25,-40],
             "type":"bar"
         }
     ],
     "layout":{
         "height":400,
         "width":400,
         "barmode":"group",
-        "barnorm":"percent"
+        "barnorm":"fraction"
     }
 }