R package check fails for macos

See https://cran.r-project.org/web/checks/check_results_stressaddition.html.

── 1. Failure: lc values have not changed (@test-lc.R#88) ─────────────────────
lc(model, "survival_tox_env_LL5", 3.14159) not equal to list(response = 28.73466, concentration = 0.7267524).
Component "concentration": Mean relative difference: 0.0002779938

Affected platforms: "r-release-macos-x86_64" and "r-oldrel-macos-x86_64"

• Check it myself for macos using rhub::check().
• Fix it by reducing the accuracy of those tests to two significant figures.
• Check again using rhub::check(platform = c("macos-highsierra-release", "macos-highsierra-release-cran")).
• Check using rhub::check_for_cran()

Must be done asap to ensure the package remains on CRAN.