Fix: Use NOP instead of void in unless macro

The `unless` macro's expansion was updated to use `...` (NOP) instead of
`void`. This change also involved removing the `void` keyword from the
parser, as it is no longer used.

src/ast/parser.rs

@@ -92,7 +92,6 @@ impl<'a> Parser<'a> {
             TokenKind::Identifier(id) => {
                 match id.as_ref() {
                     "..." => UntypedKind::Nop,
-                    "void" => UntypedKind::Constant(Value::Void),
                     _ => UntypedKind::Identifier(id.into()),
                 }
             }