Fixed the line seperator bug between colorLegend and SizeLegend in scatterplot charts

[Anubhav-2003]

Issue it fixes: #2735

What kind of change does this PR introduce:
It fixes the line seperator bug between ColorLegend and SizeLegend in the scatterplot charts.

[Anubhav-2003]

@sophiamersmann Kindly review my PR and approve it. Thank you.

[sophiamersmann]

Hey @Anubhav-2003

Thank you for your contribution!

The check that you added almost gets us there. In a few instances, the separator line is also removed for charts that have both a colour and a size legend. Check out this chart, for example. It would be better to rely on legendItems or even legendDimensions itself to determine whether the colour legend is present or not.

Additionally, it would be nice to remove the extra padding that is only needed when the colour legend is present. The y-position of the size legend is defined here:

owid-grapher/packages/@ourworldindata/grapher/src/scatterCharts/ScatterPlotChart.tsx

Line 742 in 91ad2fc

const sizeLegendY = bounds.top + legendDimensions.height + 16

It would be great if you could update sizeLegendY such that the size legend is rendered at the very top if the colour legend is not displayed.

[Anubhav-2003]

@sophiamersmann I have tried to implement the changes according to your instructions. Please review my changes. Thank You.

[sophiamersmann]

Looking good! I'll merge this code into master now. Thanks again for your contribution!