fix isVoid return type

yjhmelody · yjhmelody · commit adcf3b4cacbc · 2021-03-19T11:37:30.000+08:00
diff --git a/std/assembly/builtins.ts b/std/assembly/builtins.ts
@@ -54,7 +54,7 @@ export declare function isManaged<T>(value?: T): bool;
 
 // @ts-ignore: decorator
 @builtin
-export declare function isVoid<T>(): boolean;
+export declare function isVoid<T>(): bool;
 
 // @ts-ignore
 @builtin
