Fix remaining acceptance tests to be V3-compatible

examples/acceptance_tests/077/validators/spend2.ak

@@ -3,15 +3,19 @@ use cardano/transaction.{Output, Transaction}
 
 validator foo {
   spend(
-    _datum: Void,
+    _datum: Option<Void>,
     _redeemer: Void,
     _ref: Data,
     transaction: Transaction,
-  ) -> Bool {
+  ) {
     expect Some(_) = list.find(transaction.outputs, fn(_) { True })
     let _ = find_stuff(transaction)
     True
   }
+
+  else(_) {
+    fail
+  }
 }
 
 fn find_stuff(transaction: Transaction) -> Output {