Reduce log noise for AbstractCorrelatingMH

We use an aggregate handler that uses a group timeout.
It's expected that this timeout will be hit frequently.
However, this causes a info log message emitted every time.
I'd propose to log this message on debug.

**Cherry-pick to `6.1.x` & `6.0.x`**

spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractCorrelatingMessageHandler.java

@@ -863,7 +863,7 @@ public abstract class AbstractCorrelatingMessageHandler extends AbstractMessageP
 	}
 
 	protected void expireGroup(Object correlationKey, MessageGroup group, Lock lock) {
-		this.logger.info(() -> "Expiring MessageGroup with correlationKey[" + correlationKey + "]");
+		this.logger.debug(() -> "Expiring MessageGroup with correlationKey[" + correlationKey + "]");
 		if (this.sendPartialResultOnExpiry) {
 			this.logger.debug(() -> "Prematurely releasing partially complete group with key ["
 					+ correlationKey + "] to: " + getOutputChannel());