Merge pull request #174010 from teto/pgadmin-mainProgram

pgadmin: set mainProgram

pkgs/tools/admin/pgadmin/default.nix

···
     license = licenses.mit;
     changelog = "https://www.pgadmin.org/docs/pgadmin4/latest/release_notes_${lib.versions.major version}_${lib.versions.minor version}.html";
     maintainers = with maintainers; [ gador ];
+    mainProgram = "pgadmin4";
   };
 }