Replace size by linewidth

[mayer79]

ggplot2 has deprecated the size argument to determine line width. The new argument is called linewidth.

This PR deals with this aspect of issue `#576

• Out of scope of this PR: Change {ingredients}
• Fix additional deprecations, e.g. the use of aes_string().

[hbaniecki]

Thanks! Let's see if the tests start working again on main

[pbiecek]

thanks guys!