hplip: udev rule: drop `nohup` instead of patching it

hplip's udev rule uses `nohup` to attempt to detach
its printer configuration script from the udev process.
However, this attempt is futile as udev
tracks its child processes with cgroups:
https://unix.stackexchange.com/a/243648

The hardcoded path to `nohup` was patched to use Nix' `nohup`.
This commit alters the patch script so
that it simply drops the call to `nohup`.