system-config-printer: unbreak dbus service (again)

The service file refers to /usr/bin/... instead of a Nix store path.
Fix it.

The original fix was wrongly removed in commit 03353ce6ff
("system-config-printer: 1.3.12 -> 1 5.7"). We can remove this fixup on
the _next_ upstream release.

pkgs/tools/misc/system-config-printer/default.nix

@@ -53,6 +53,9 @@ in stdenv.mkDerivation rec {
       ( cd $out/share/system-config-printer/troubleshoot
         mv .__init__.py-wrapped __init__.py
       )
+
+      # The below line will be unneeded when the next upstream release arrives.
+      sed -i -e "s|/usr/bin|$out/bin|" "$out/share/dbus-1/services/org.fedoraproject.Config.Printing.service"
     '';
 
   meta = {