farbfeld: 3 -> 4

pkgs/development/libraries/farbfeld/default.nix

···
 
 stdenv.mkDerivation rec {
   name = "farbfeld-${version}";
-  version = "3";
+  version = "4";
 
   src = fetchgit {
     url = "https://git.suckless.org/farbfeld";
     rev = "refs/tags/${version}";
-    sha256 = "1k9cnw2zk9ywcn4hibf7wgi4czwyxhgjdmia6ghpw3wcz8vi71xl";
+    sha256 = "0pkmkvv5ggpzqwqdchd19442x8gh152xy5z1z13ipfznhspsf870";
   };
 
   buildInputs = [ libpng libjpeg ];