Removed promote-until-clean because it moves the file out of _build instead of copying it, which causes issues for the gitlab build

src/stages/adt_generator/dune

@@ -2,7 +2,8 @@
   (target fold.ml)
   (deps generator.py)
   (action (with-stdout-to fold.ml (run python3 ./generator.py)))
-  (mode (promote (until-clean))))
+;  (mode (promote (until-clean))) ; If this is uncommented, then "dune build -p ligo" can't find the file (but "dune build" can)
+)
 ; (library
 ;   (name adt_generator)
 ;   (public_name ligo.adt_generator)