Fix helpers import

Previously we referred to "./default" when we should have referred to
"./default.nix" or "./"

Change-Id: I513634165a034043de4e4a23a873022ec26ade1e
diff --git a/flake.nix b/flake.nix
index 1dcca7b..5f0f5fe 100644
--- a/flake.nix
+++ b/flake.nix
@@ -2,6 +2,6 @@
   description = "Clicks helpers for writing boilerplatey nix";
 
   outputs = { self, nixpkgs }: {
-    helpers = import ./default;
+    helpers = import ./;
   };
 }