lightdm: 1.26.0 -> 1.28.0

Semi-automatic update generated by
https://github.com/ryantm/nixpkgs-update tools. This update was made
based on information from
lightdm

pkgs/applications/display-managers/lightdm/default.nix

···
 
 stdenv.mkDerivation rec {
   pname = "lightdm";
-  version = "1.26.0";
+  version = "1.28.0";
 
   name = "${pname}-${version}";
 
···
     owner = "CanonicalLtd";
     repo = pname;
     rev = version;
-    sha256 = "1mhj6l025cnf2dzxnbzlk0qa9fm4gj2aw58qh5fl4ky87dp4wdyb";
+    sha256 = "1mmqy1jdvgc0h0h9gli7n4vdv5p8m5019qjr5ni4h73iz6mjdj2b";
   };
 
   nativeBuildInputs = [