Fix typo

Author: bglgwyng

nix/modules/project/settings/all.nix

@@ -420,7 +420,7 @@ in
     custom = {
       type = types.functionTo types.package;
       description = ''
-        A custom funtion to apply on the Haskell package.
+        A custom function to apply on the Haskell package.
 
         Use this only if none of the existing settings are suitable.