Bump testthat version

Author: lionel-

DESCRIPTION

@@ -30,7 +30,7 @@ Imports:
     htmltools,
     lifecycle,
     rlang,
-    testthat (>= 3.0.2.9001),
+    testthat (>= 3.0.3),
     xml2 (>= 1.0.0)
 Suggests:
     covr,
@@ -39,8 +39,6 @@ Suggests:
     withr
 LinkingTo:
     cpp11
-Remotes:
-    r-lib/testthat
 RoxygenNote: 7.1.1.9001
 Roxygen: list(markdown = TRUE)
 URL: https://vdiffr.r-lib.org/, https://github.com/r-lib/vdiffr