delete scale name tests

[teunbrand]

Hello there,

We have been preparing a new release of ggplot2 and during a reverse dependency check, it became apparent that the prospective ggplot2 3.5.0 would break viridis.

Briefly, the scale_name field in scales is now deprecated. The tests that checked the scale name have thus become superfluous, but would still register as broken. This PR deletes the tests that the scale name.

To test the code changes with the release candidate, you can install it with the code below:

remotes::install_github("tidyverse/ggplot2", ref = remotes::github_pull("5592"))

The release of ggplot2 3.5.0 is scheduled for the 12th of February. The progress of the release can be tracked in tidyverse/ggplot2#5588. We hope that this PR might help viridis get out a fix if necessary.

[sjmgarnier]

@teunbrand Thanks! I will review the changes and push a new version of viridis to CRAN over the weekend.

[teunbrand]

Thanks for the prompt response!