`scale_color_gradient()`: `guide='legend'` is rendered as a colorbar

[ASmirnov-HORIS]

Example:

values = [1, 2, 3]
ggplot() + \
    geom_point(aes(x=values, color=values)) + \
    scale_color_gradient(guide='legend')

Output:

Expected (as in v4.3.0):