[Types] Wrong recursion in Mark’s _tip_ option

[mwaibel-go]

MarkOption.tip is of type TipOptions. (This is a simplified statement, but true enough for this issue description).

TipOptions itself derives from MarkOptions.

This recursion lets us specify nested tips:

Plot.dot(penguins, {x: "culmen_length_mm", y: "culmen_depth_mm", tip: {tip: {tip: {tip: {tip: {tip: {}}}}}}}).plot()

TipOptions should probably exclude the tip property.

Related: #2423