Drops checks added with register_check(). With no argument, clears the whole
registry.
Examples
register_check("tmp", function(path, verbose = TRUE) {
checktor_check_result(TRUE, character(0), "noop")
})
unregister_check("tmp")
registered_checks()
#> [1] check category severity
#> <0 rows> (or 0-length row.names)