fix rotate_callback demo

Signed-off-by: Nyaozhupeng <yaozhupeng@huawei.com>

zh-cn/application-dev/reference/apis/js-apis-image.md

@@ -735,9 +735,15 @@ rotate(angle: number, callback: AsyncCallback\<void>): void
 **示例：**
 
 ```js
-async function Demo() {
-	await pixelmap.rotate(90.0);
-}
+var angle = 90.0;
+pixelmap.rotate(angle, (err) => {
+	if (err) {
+        console.error("Failed to set rotation.");
+        return;
+    } else {
+        console.log("Succeeded in setting rotation.");
+	}
+})
 ```
 
 ### rotate<sup>9+</sup>