Remove outdated advice on producing Haskell file

doc/tutorial/gf-tutorial.t2t

@@ -4737,10 +4737,6 @@ abstract Query = {
 
 To make it easy to define a transfer function, we export the
 abstract syntax to a system of Haskell datatypes:
-```
-  % gf --output-format=haskell Query.pgf
-```
-It is also possible to produce the Haskell file together with PGF, by
 ```
   % gf -make --output-format=haskell QueryEng.gf
 ```