Fix a warning "... may be used in an incorrect context"

[yutannihilation]

A small followup of #4868.

I found this warning on our CI.

* checking R code for possible problems ... NOTE
Warning: Warning: <anonymous>: ... may be used in an incorrect context: ‘list(...)’ (/home/runner/work/ggplot2/ggplot2/check/ggplot2.Rcheck/00_pkg_src/ggplot2/R/save.r:176)
plot_dev: ... may be used in an incorrect context: ‘list(...)’
  (/home/runner/work/ggplot2/ggplot2/check/ggplot2.Rcheck/00_pkg_src/ggplot2/R/save.r:176)
Warning: Warning: <anonymous>: ... may be used in an incorrect context: ‘list(...)’ (/home/runner/work/ggplot2/ggplot2/check/ggplot2.Rcheck/00_pkg_src/ggplot2/R/save.r:176)

Looking at the corresponding line before vctrs, I guess this was the intention.

ggplot2/R/save.r

Line 176 in 7571122

dev <- function(...) do.call(device, modify_list(list(...), call_args))

[thomasp85]

LGTM - good catch