Use overlay

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

packages/docker/shlink/default.nix

@@ -1,12 +1,5 @@
-{
-  pkgs,
-  inputs,
-  system,
-  ...
-}:
+{ pkgs, ... }:
 let
-  selfPkgs = inputs.self.packages.${system};
-
   php = pkgs.php84.buildEnv {
     extensions =
       { all, ... }:
@@ -32,7 +25,7 @@ let
 
   shlink = pkgs.runCommandLocal "shlink" { } ''
     mkdir -p $out/var/www
-    cp -r ${selfPkgs.shlink} $out/var/www/shlink
+    cp -r ${pkgs.shlink} $out/var/www/shlink
 
     rr_config_path="$out/var/www/shlink/config/roadrunner/.rr.yml"
     original_mode="$(stat -c "%a" "$rr_config_path")"