GH-3142: Clarify republishToDlq default behaviour in docs

The previous description opened with "By default, messages that fail after
retries are exhausted are rejected", which implies the default is false
(reject). The actual default is true (republish with extra headers).

Rewrite the description to lead with the true default behaviour and
describe the false case explicitly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: won-seoop

docs/modules/ROOT/pages/rabbit/rabbit_overview/rabbitmq-consumer-properties.adoc

@@ -272,9 +272,8 @@ When `republishToDlq` is `true`, specifies the delivery mode of the republished
 +
 Default: `DeliveryMode.PERSISTENT`
 republishToDlq::
-By default, messages that fail after retries are exhausted are rejected.
-If a dead-letter queue (DLQ) is configured, RabbitMQ routes the failed message (unchanged) to the DLQ.
-If set to `true`, the binder republishs failed messages to the DLQ with additional headers, including the exception message and stack trace from the cause of the final failure.
+When set to `true` (the default), the binder republishes failed messages to the dead-letter queue (DLQ) with additional headers, including the exception message and stack trace from the cause of the final failure.
+When set to `false`, messages that fail after retries are exhausted are rejected; if a dead-letter queue is configured, RabbitMQ then routes the rejected message (unchanged, without extra headers) to the DLQ.
 Also see the xref:rabbit/rabbit_overview/rabbitmq-consumer-properties.adoc#spring-cloud-stream-rabbit-frame-max-headroom[frameMaxHeadroom property].
 +
 Default: `true`