nixosTests.systemd-confinement: fix script format

https://hydra.nixos.org/build/142591177/nixlog/30

ZHF: #122042

Changed files
+2 -1
nixos
+2 -1
nixos/tests/systemd-confinement.nix
···
"chroot-exec chown 65534 /bin",
)
machine.succeed(
-
'test "$(chroot-exec id -u)" = 0', "chroot-exec chown 0 /bin",
+
'test "$(chroot-exec id -u)" = 0',
+
"chroot-exec chown 0 /bin",
)
'';
}