Don't build a superfluous list

Co-authored-by: Sasha Lopoukhine <superlopuh@gmail.com>

xdsl/irdl/irdl.py

@@ -255,7 +255,7 @@ def get_resolved_variables(self) -> set[str]:
         if len(self.attr_constrs) == 0:
             return set()
         return set[str].intersection(
-            *[constr.get_resolved_variables() for constr in self.attr_constrs]
+            *(constr.get_resolved_variables() for constr in self.attr_constrs)
         )