since vesion 1.30， can not get trace.id from MDC

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## Describe the bug
since vesion 1.30， can not get trace.id from MDC

## Steps to reproduce
```
@ControllerAdvice
@Slf4j
public class GlobalResponseBodyAdvice implements ResponseBodyAdvice {
@Override
public boolean supports(MethodParameter returnType, Class> converterType) {
return true;
}

@Override
public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
log.info("trace.id:{}", MDC.get("trace.id"));
return body;
}
}
```

agent jar: elastic-apm-agent-1.30.1.jar or after this version
call MDC.get("trace.id"), it returns null

agent jar: elastic-apm-agent-1.29.0.jar
call MDC.get("trace.id"), it returns the correct string

## Expected behavior

call MDC.get("trace.id"), it should return the correct string.

or how can I get correct string

## Debug logs

Click to expand

```
replace this line with your debug logs
```