Remove failing 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 ghibli.

This PR fixes failing tests by removing them. For context, we have deprecated the scale_name argument and the tests were checking whether an error was throws if the scale_name argument is missing. Having a missing scale_name field is the new default, so these tests no longer serve their purpose.

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 https://github.com/tidyverse/ggplot2/issues/5588. We hope that this PR might help ghibli get out a fix if necessary.