Warning: Using `size` aesthetic for lines was deprecated in ggplot2 3.4.0

Hi,

Thank you for this very nice package.

Here is a minor issue caused by a deprecated feature:

``` r
library(tidyverse)
library(ggupset)
tidy_movies %>%
distinct(title, year, length, .keep_all=TRUE) %>%
ggplot(aes(x=Genres)) +
geom_bar() +
scale_x_upset(n_intersections = 20)
#> Warning: Removed 100 rows containing non-finite outside the scale range
#> (`stat_count()`).
#> Warning: Using `size` aesthetic for lines was deprecated in ggplot2 3.4.0.
#> ℹ Please use `linewidth` instead.
#> ℹ The deprecated feature was likely used in the ggupset package.
#> Please report the issue at .
#> This warning is displayed once per session.
#> Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
#> generated.
```

^{Created on 2026-07-13 with [reprex v2.1.1](https://reprex.tidyverse.org)}

I'm using ggupset 0.4.1 and ggplot2 4.0.3

Reproduce the provided R example using ggupset 0.4.1 and ggplot2, then search the ggupset package for the deprecated `size` aesthetic. Confirm the change by rerunning the example and checking that the `linewidth` deprecation warning no longer appears.

Written by the indexing model from the issue text.