geom_dumbbell: change parameter size to linewidth

[braunerphilipp]

geom_dumbbell seems not to be upgraded to ggplot2 3.4.0 yet.
When I use geom_dumbbell with the size parameter to set the linewidth, the resulting diagram is rendered correctly, but I get a warning message. If I change the size parameter to linewidth, the parameter seems to be ignored (diagram is rendered with the default linewidth).

I tried both ggalt 0.4.0 and the current dev version.

Using the `size` aesthietic with geom_segment was deprecated in ggplot2 3.4.0.
ℹ Please use the `linewidth` aesthetic instead.