Showline not cleaned up properly

Similar to #2392 ...

```javascript
Plotly.newPlot(gd,
    [{y: [1,2,3]}, {y: [10, 30, 20]}],
    {yaxis: {showline: true}}
);
Plotly.relayout(gd, {'yaxis.showline': false});
```

Results in the y-axis line still being shown.

Ref https://github.com/plotly/react-plotly.js/issues/53