lib: drop nmd helpers

lib/default.nix

@@ -3,6 +3,5 @@
   booleans = import ./booleans.nix {inherit lib;};
   types = import ./types {inherit lib;};
   languages = import ./languages.nix {inherit lib;};
-  nmd = import ./nmd.nix;
   lua = import ./lua.nix {inherit lib;};
 }

lib/stdlib-extended.nix

@@ -70,5 +70,4 @@ in
 
     # For forward compatibility.
     literalExpression = super.literalExpression or super.literalExample;
-    literalDocBook = super.literalDocBook or super.literalExample;
   })