Remove unnecessary calls to Reference::clear

Prior to this commit, `ConcurrentReferenceHashMap` subclasses extending
`Reference` would call `Reference::clear` right next to
`Reference::enqueue`; this is not needed as the latter calls it already.

Closes gh-28863

spring-core/src/main/java/org/springframework/util/ConcurrentReferenceHashMap.java

@@ -1046,7 +1046,6 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
 		@Override
 		public void release() {
 			enqueue();
-			clear();
 		}
 	}
 
@@ -1083,7 +1082,6 @@ public class ConcurrentReferenceHashMap<K, V> extends AbstractMap<K, V> implemen
 		@Override
 		public void release() {
 			enqueue();
-			clear();
 		}
 	}