Update grammar_grapher with the new forced (&&) directive (#31704)

Author: lucach

Tools/peg_generator/scripts/grammar_grapher.py

@@ -29,6 +29,7 @@
 from pegen.grammar import (
     Alt,
     Cut,
+    Forced,
     Grammar,
     Group,
     Leaf,
@@ -60,6 +61,8 @@ def references_for_item(item: Any) -> List[Any]:
         return [_ref for _item in item.items for _ref in references_for_item(_item)]
     elif isinstance(item, Cut):
         return []
+    elif isinstance(item, Forced):
+        return references_for_item(item.node)
     elif isinstance(item, Group):
         return references_for_item(item.rhs)
     elif isinstance(item, Lookahead):