Fix a misleading style in the example (#5660)

Author: kkshinkai

beta/src/content/learn/javascript-in-jsx-with-curly-braces.md

@@ -469,7 +469,7 @@ export default function TodoList() {
 ```css
 body { padding: 0; margin: 0 }
 body > div > div { padding: 20px; }
-.avatar { border-radius: 50%; height: 90px; }
+.avatar { border-radius: 50%; }
 ```
 
 </Sandpack>
@@ -584,4 +584,4 @@ Variables and functions can help you keep the markup simple!
 
 </Solution>
 
-</Challenges>
+</Challenges>