Fix issues from dev lintr

[MichaelChirico]

Thank you for using {lintr}!

The development version of lintr breaks {box.linters} in two ways:

• We require the message component of Lint() objects to be a plain character, in particular, not a {glue} object.
• The default pipe in the Tidyverse guide is now |>, not %>%, so code using %>% can newly lint: https://style.tidyverse.org/pipes.html#introduction

The latest release of {testthat} broke {lintr}, so I'll be releasing a breaking change in the near future, which this PR resolves.

[radbasa]

Approved in principle.

lintr@3.2.0, testthat@3.2.3

lintr@3.2.0, testthat@3.3.1

We will need to re-test when lintr gets updated.

[radbasa]

lintr@3.3.0.1 released last week.
box@1.2.1 released during the weekend.

This PR/branch fails because it does not yet have the fix from #184.

Manually applying the fix from #184: