libcamera: use udev, not systemd

As the comment indicated, the only part of systemd that was used is
udev.  This should decrease the closure size, and also do the right
thing on platforms with different udev implementations.

pkgs/by-name/li/libcamera/package.nix

@@ -16,7 +16,7 @@
   doxygen,
   python3,
   python3Packages,
-  systemd, # for libudev
+  udev,
   libpisp,
   withTracing ? lib.meta.availableOn stdenv.hostPlatform lttng-ust,
   lttng-ust, # withTracing
@@ -76,7 +76,7 @@ stdenv.mkDerivation rec {
       libdrm
 
       # hotplugging
-      systemd
+      udev
 
       # pycamera
       python3Packages.pybind11