try fix mac os test by changing expected value to computed relative path

as when getwd() and tmpdir() are on different drive, this could lead to issues

Author: cderv

tests/testthat/test-utils-projects.R

@@ -3,11 +3,14 @@ test_that("project_path() works with explicit root", {
   withr::local_dir(temp_dir)
   expect_identical(
     project_path("data", "file.csv", root = temp_dir),
-    file.path("data", "file.csv")
+    xfun::relative_path(file.path("data", "file.csv"), dir = temp_dir)
   )
   expect_identical(
     project_path("outputs", "figures", "plot.png", root = temp_dir),
-    file.path("outputs", "figures", "plot.png")
+    xfun::relative_path(
+      file.path("outputs", "figures", "plot.png"),
+      dir = temp_dir
+    )
   )
   expect_identical(project_path(root = temp_dir), ".")
 })