Marker: closed marker shapes should disable outlines by default

Otherwise things like scatter plots have markers with black outlines

![asis_gridAdvanced](https://github.com/ScottPlot/ScottPlot/assets/4165489/6178a24c-0aec-4ece-8c40-bb2242b3bfb7)
