Switch swap building fff to nix

nvim/lua/plugs/fff.lua

@@ -1,10 +1,6 @@
 return {
     "dmtrKovalenko/fff.nvim",
-    build = function()
+    build = "nix run .#release",
-        -- this will download prebuild binary or try to use existing rustup toolchain to build from source
-        -- (if you are using lazy you can use gb for rebuilding a plugin if needed)
-        require("fff.download").download_or_build_binary()
-    end,
     lazy = false,
     keys = {
         {