mas: use testers.testVersion

pkgs/os-specific/darwin/mas/default.nix

···
 , stdenvNoCC
 , fetchurl
 , installShellFiles
-, testVersion
+, testers
 , mas
 }:
 
···
   '';
 
   passthru.tests = {
-    version = testVersion {
+    version = testers.testVersion {
       package = mas;
       command = "mas version";
     };