Do not add covr to Suggests in use_coverage()

[Bisaloo]

Context

At the moment, use_coverage() adds covr to Suggests. This was not always the case but it was added in 2698067, apparently to facilitate coverage computation in travis CI(?).

usethis and the R community have now largely moved away from travis in favour of GitHub Actions. The test-coverage GHA workflow provided by usethis already installs covr in all cases, without needing it to be explicitly listed in Suggests.

usethis/.github/workflows/test-coverage.yaml

Lines 24 to 27 in e05947f

	- uses: r-lib/actions/setup-r-dependencies@v2
	with:
	extra-packages: any::covr
	needs: coverage

Homogenizing

This PR proposes to stop automatically including covr in Suggests when running use_coverage() (fix #1844). This is in line with what use_pkgdown() does: pkgdown is not added to Suggests there. Again, it's not necessary because as in the test-coverage workflow, pkgdown is automatically installed without the need to l

Differences with use_pkgdown()

use_pkgdown() does however use check_installed("pkgdown"). I don't believe it's necessary in the case of use_coverage(). The difference is that use_pkgdown() needs to know which pkgdown version is installed to determine the structure of the default _pkgdown.yml config file.

usethis/R/pkgdown.R

Lines 50 to 52 in 00ee947

	if (pkgdown_version() >= "1.9000") {
	config$template <- list(bootstrap = 5L)
	}

(Note that check_installed("pkgdown") could probably be removed here as well though. It was strictly necessary in the past when usethis used pkgdown functions (87a2cb5) but it's not the case anymore as far as I can tell. Version checking could be done conditionally and the bootstrap 5 template could be used by default when pkgdown is not yet installed. It's a different question though and I can open a separate issue if you wish)

[jennybc]

Thanks!