chore(doc): fix example (#1657)

## What does this PR do?
fix example code error.

![image](https://github.com/apache/incubator-fury/assets/46479343/eafd5068-7aa0-4cde-af31-ef23b4fc9f55)



## Related issues



## Does this PR introduce any user-facing change?
- [ ] Does this PR introduce any public API change?
- [ ] Does this PR introduce any binary protocol compatibility change?


## Benchmark

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README.md

@@ -175,6 +175,9 @@ public class Example {
         // but may be insecure if the classes contains malicious code.
         .requireClassRegistration(true)
         .buildThreadSafeFury();
+      // Registering types can reduce class name serialization overhead, but not mandatory.
+      // If class registration enabled, all custom types must be registered.
+      fury.register(SomeClass.class);
       byte[] bytes = fury.serialize(object);
       System.out.println(fury.deserialize(bytes));
     }