px.line: don't use webgl if line_shape="spline" is given

[bwest2397]

The documentation for documentation for plotly.express.line seems to imply that when calling px.line, line_shape can be given as "linear" or "spline" without any other limitations. However, if one calls it with render_mode="auto" (or without providing render_mode, as "auto" is its default value) and with a large enough dataframe (over 1000 total plotted entries), line_shape="spline" causes an error. This error is caused by the webgl render mode (go.Scattergl) being used by default with large dataframes instead of the svg render mode (go.Scatter). This PR works around this issue by not defaulting to the webgl render mode is line_shape="spline" is given, as the documentation implies that this should work. It's worth noting that this will likely incur a performance penalty, but I think that anyone rendering that much data is willing to accept the hit :)

This should address #2812

Code PR

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[alexcjohnson]

@bwest2397 thanks for this, looks great and apologies for letting it sit so long. Would you add a line in the changelog under unreleased/fixed? Then we'll merge!

[bwest2397]

@bwest2397 thanks for this, looks great and apologies for letting it sit so long. Would you add a line in the changelog under unreleased/fixed? Then we'll merge!

@alexcjohnson Done. Assuming you agree with the content of the changelog message, feel free to merge when you're ready.

[alexcjohnson]

💃