Use of multiple aesthetics in scale_*_manual causes legend to be dropped in ggplotly conversion

[MilesMcBain]

Feels related to #2466.

If the {ggplot2} facility to bind a custom scale to muiltiple aesthetics is used, the legend is dropped when the plot is converted plotly.

Reprex:

library(plotly)
library(ggplot2)
library(palmerpenguins)

p <-
  penguins |>
  ggplot(aes(
    x = body_mass_g,
    y = bill_length_mm,
    colour = species,
    fill = species
  )) +
  geom_point() +
  scale_colour_manual(
    values = c(
        "Adelie" = "red",
        "Chinstrap" = "green",
        "Gentoo" = "blue"
    ),
    aesthetics = c("colour", "fill")
  )

ggplotly(p)
# plot has no legend

Legend appears if we remove references to "fill" and only use "colour".