Switch `size` aes to `linewidth`

[quantixed]

This issue is just to report the warning I get when generating a density plot with ggcyto().

I am using {ggcyto} 1.37.1 (from GitHub) and {ggplot2} 4.0.0

Warning messages:
1: Using the `size` aesthetic with geom_segment was deprecated in ggplot2 3.4.0.
ℹ Please use the `linewidth` aesthetic instead.
ℹ The deprecated feature was likely used in the ggcyto package.
  Please report the issue to the authors.
This warning is displayed once every 8 hours.
Call `lifecycle::last_lifecycle_warnings()` to see where this warning was generated. 
2: `label` cannot be a <ggplot2::element_blank> object.