fix: unused import error

Author: Yiğit Can Başalma

api/src/main/java/org/apache/cloudstack/backup/BackupManager.java

@@ -32,7 +32,6 @@
 import org.apache.cloudstack.api.command.user.backup.ListBackupsCmd;
 import org.apache.cloudstack.api.response.BackupResponse;
 import org.apache.cloudstack.framework.config.ConfigKey;
-import org.apache.cloudstack.framework.config.ValidatedConfigKey;
 import org.apache.cloudstack.framework.config.Configurable;
 
 import com.cloud.exception.ResourceUnavailableException;