deadpixi-sam: remove duplicate alias

It is already listed in aliases.nix, and I managed to get this from Nix:

  error: Alias deadpixi-sam is still in all-packages.nix

Fixes: 218d81b ("all-packages: move aliases to aliases.nix")

pkgs/top-level/all-packages.nix

@@ -14085,7 +14085,6 @@ in
   spamassassin = callPackage ../servers/mail/spamassassin { };
 
   deadpixi-sam-unstable = callPackage ../applications/editors/deadpixi-sam { };
-  deadpixi-sam = deadpixi-sam-unstable;
 
   samba3 = callPackage ../servers/samba/3.x.nix { };