hello: doCheck = true; again

Close #17573.

pkgs/applications/misc/hello/default.nix

···
     sha256 = "0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i";
   };
 
-  doCheck = false;
+  doCheck = true;
 
   meta = {
     description = "A program that produces a familiar, friendly greeting";