Add note to watch examples

Author: jay-es

src/guide/essentials/watchers.md

@@ -46,6 +46,10 @@ export default {
 <p>{{ answer }}</p>
 ```
 
+:::info
+The above code may cause race conditions, but the cleanup process is omitted for simplicity.
+:::
+
 [Try it in the Playground](https://play.vuejs.org/#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)
 
 The `watch` option also supports a dot-delimited path as the key:
@@ -97,6 +101,10 @@ watch(question, async (newQuestion, oldQuestion) => {
 </template>
 ```
 
+:::info
+The above code may cause race conditions, but the cleanup process is omitted for simplicity.
+:::
+
 [Try it in the Playground](https://play.vuejs.org/#eNplkkGPmzAQhf/KKxdA3Rj1mpJUUdVDT22lHrlYxDRuYOzaJjRC/PcdxyGr3b2A7PfmmzcMc3awVlxGlW2z2rdO2wCvwmj3DenBGhcww6nuCZMM7QkLOmcG5FyRN9RQa8gH/BuVD9oQdtFb5Hm5KpL8pNx6/+vu8xj9KPv+CnYFqQnyhTFIdxb4vCkjpaFb32JVnyD9lVoUpKaVVmK3x9wQoLtXgtB0VP9/cOMveYk9Np/K5MM9l7jIflScLv990nTW9EcIwXNFR3DX1YwYk4dxyrNXTlIHdCrGyk8hWL+tqqvyZMQUukpaHYOnujdtilTLHPHXGyrKUiRH8i9obx+5UM4Z98j6Pu23qH/AVzP2R5CJRMl14aRw+PldIMdH3Bh3bnzxY+FcdZW2zPvlQ1CD7WVQfALquPToP/gzL4RHqsg89rJNWq3JjgGXzWCOqt812ao3GaqEqRKHcfO8/gDLkq7r6tEyW54Bf5TTlg==)
 
 ### Watch Source Types {#watch-source-types}