Incorrect default DLT topic name in sample-01 Application.java

[kkminseok]

Expected Behavior

Current Behavior

Context

The default topic name generated by DeadLetterPublishingRecoverer uses -dlt suffix, not .DLT.
But in samples/sample-01/Application.java, the listener is subscribing to topic1.DLT.
This causes deserialization errors because the actual DLT topic is topic1-dlt.

5529cbb

[alexisgra]

Hi, I fixed it in #3831