Pass arguments to flake_env in the correct order

This prevents flake_env from deleting the directory containing the
.envrc file if the flake specifier is ".". In 7759d2a, the order of the
arguments was swapped:

In bin/flake_env.re
-      let flake_specifier = argv[1];
-      let layout_directory = argv[2];

In lib/flake_env__util.re
+    let layout_directory = argv[1];
+    let flake_specifier = argv[2];

but the direnvrc was not updated to match.

Fixes: 7759d2ac6a

direnvrc

@@ -41,7 +41,7 @@ use_flake_env() {
   local ld=$(direnv_layout_dir)
   export direnv
 
-  eval "$(@flake_env@ "${1:-"."}" "$ld")"
+  eval "$(@flake_env@ "$ld" "${1:-"."}")"
 
   export -n direnv