scattermapbox.line.width is not supported but it is in `_fullData`

[chriddyp]

In our plotly.py 3.0.0r4 (plotly/plotly.py#942), we can view the default properties in jupyter notebooks. Today, we noticed that scattermapbox.line.width appears even though it isn't a supported property.

Codepen: https://codepen.io/chriddyp/pen/mKmaQv?editors=0011

(Previously, if properties appeared in _fullData that weren't in the schema the plotly.py validation would raise an exception. This was fixed in plotly/plotly.py@3d0460e so plotly.py is no longer blocked by this artifact).

[alexcjohnson]

Seems to be a hack to make legends happy. Should be easy to unwind on the legend side.

plotly.js/src/traces/scattermapbox/defaults.js

Lines 46 to 47 in 1a050e8

	// we need mock marker.line object to make legends happy
	marker.line = {width: 0};