Fix unit tests for sf labels

[thomasp85]

Upstream updates have broken some of our unit tests

https://cran.r-project.org/web/checks/check_results_ggplot2.html

[paleolimbot]

If I'm understanding the failure properly, I just fixed (and merged) this in #3378.

[lock]

This old issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with reprex) and link to this issue. https://reprex.tidyverse.org/