rm useless attrs in test mock

Author: etpinard

test/image/mocks/violin_box_multiple_widths.json

@@ -3,57 +3,33 @@
             "type": "violin",
             "width": 0.315,
             "x": [0, 5, 7, 8],
-            "points": "none",
             "side": "positive",
-            "box": {
-              "visible": false
-            },
-            "boxpoints": false,
             "line": {
                 "color": "black"
             },
             "fillcolor": "#8dd3c7",
             "opacity": 0.6,
-            "meanline": {
-                "visible": false
-            },
             "y0": 0.0
         }, {
             "type": "violin",
             "x": [0, 5, 7, 8],
-            "points": "none",
             "side": "positive",
-            "box": {
-              "visible": false
-            },
-            "boxpoints": false,
             "line": {
                 "color": "black"
             },
             "fillcolor": "#d3c78d",
             "opacity": 0.6,
-            "meanline": {
-                "visible": false
-            },
             "y0": 0.1
         }, {
             "type": "box",
             "width": 0.5421,
             "x": [0, 5, 7, 8],
-            "points": "none",
             "side": "positive",
-            "box": {
-              "visible": false
-            },
-            "boxpoints": false,
             "line": {
                 "color": "black"
             },
             "fillcolor": "#c78dd3",
             "opacity": 0.6,
-            "meanline": {
-                "visible": false
-            },
             "y0": 0.2
     }],
     "layout": {