remove duplicate keys from two mocks

Author: archmoj

test/image/mocks/8.json

@@ -1256,7 +1256,6 @@
             "size": 12,
             "color": "grey"
         },
-        "showlegend": true,
         "width": 500,
         "height": 500,
         "margin": {

test/image/mocks/matching-missing-axes.json

@@ -45,7 +45,6 @@
       "alignmentgroup": "True",
       "offsetgroup": "smoker=No",
       "legendgroup": "smoker=No",
-      "showlegend": false,
       "marker": { "color": "#636efa" },
       "x": [ "Male", "Female", "Male" ],
       "y": [ 22.49, 22.75, 12.46 ],