Fix: restore error log level in onFailure callback

Revert the log level in onFailure from debug back to error, as
this callback handles exchange processing failures which should
not be silently swallowed at debug level.

Addresses review comment from @Croway.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: nkokitkar

components/camel-paho/src/main/java/org/apache/camel/component/paho/PahoConsumer.java

@@ -162,7 +162,7 @@ public void onComplete(Exchange exchange) {
 
                 @Override
                 public void onFailure(Exchange exchange) {
-                    LOG.debug("Rollback due to error processing Exchange ID: {}", exchange.getExchangeId(),
+                    LOG.error("Rollback due to error processing Exchange ID: {}", exchange.getExchangeId(),
                             exchange.getException());
                 }
             });