Mark applicable Scope's methods as default

Signed-off-by: Yanming Zhou <zhouyanming@gmail.com>

spring-tx/src/main/java/org/springframework/transaction/support/SimpleTransactionScope.java

@@ -81,11 +81,6 @@ public class SimpleTransactionScope implements Scope {
 		}
 	}
 
-	@Override
-	public @Nullable Object resolveContextualObject(String key) {
-		return null;
-	}
-
 	@Override
 	public @Nullable String getConversationId() {
 		return TransactionSynchronizationManager.getCurrentTransactionName();