Update SVGs for visual tests after new ggplot2 release

[jgabry]

The release candidate for ggplot2 available via remotes::install_github("tidyverse/ggplot2", ref = remotes::github_pull("5592")) breaks some of the visual tests due to very tiny differences in the SVGs. Once ggplot2 is released (scheduled for Feb 12), remember to run testthat locally and then use testthat::snapshot_review to update the SVGs. Until the ggplot2 release I will keep the SVGs compatible with the current CRAN version of ggplot2.