style does not commit changes made to `.R` files in `tests/`

[Moohan]

Describe the bug The style workflow does not commit any styled changes made to R scripts in the tests/ folder (even though styler is run against these with styler::style_pkg()). This results in an error when the tests are the only files styled, as styler makes the changes but then nothing is committed.

To Reproduce failed build

Expected behavior Style changes to the test scripts should also be committed.