[Heatmap Legend] When placed above or below chart, legend takes up a lot of unexpected space

[gvnmagni]

Legend for heatmap charts, once placed above or below the chart, are unexpectedly tall. This reduces the amount of space available for the chart itself

NOTE: I noticed this locally on a PR which hasn't been merged, I haven't got time to test if it occurs only to me, apologies if that is the case