`update_geom_defaults()` should class results

[dkahle]

Using update_geom_defaults() and update_stat_defaults() don't class the updated list, so it prints differently. Example below. Will submit simple PR to fix presently.

library("ggplot2")

GeomPoint$default_aes
#> Aesthetic mapping: 
#> * `shape`  -> 19
#> * `colour` -> "black"
#> * `size`   -> 1.5
#> * `fill`   -> NA
#> * `alpha`  -> NA
#> * `stroke` -> 0.5

str(GeomPoint$default_aes)
#> List of 6
#>  $ shape : num 19
#>  $ colour: chr "black"
#>  $ size  : num 1.5
#>  $ fill  : logi NA
#>  $ alpha : logi NA
#>  $ stroke: num 0.5
#>  - attr(*, "class")= chr "uneval"

update_geom_defaults("point", list(size = 4))

GeomPoint$default_aes
#> $size
#> [1] 4
#> 
#> $shape
#> [1] 19
#> 
#> $colour
#> [1] "black"
#> 
#> $fill
#> [1] NA
#> 
#> $alpha
#> [1] NA
#> 
#> $stroke
#> [1] 0.5

class(GeomPoint$default_aes) <- "uneval"
GeomPoint$default_aes
#> Aesthetic mapping: 
#> * `size`   -> 4
#> * `shape`  -> 19
#> * `colour` -> "black"
#> * `fill`   -> NA
#> * `alpha`  -> NA
#> * `stroke` -> 0.5

^{Created on 2023-01-11 with reprex v2.0.2}