minor: use the same naming scheme for backup folders as the old screening upgrade procedure

SVN: 23192

installation/source/java/ch/systemsx/cisd/openbis/installer/izpack/PrepareInstallationBackupAction.java

@@ -32,7 +32,7 @@ import com.izforge.izpack.data.PanelAction;
  */
 public class PrepareInstallationBackupAction implements PanelAction
 {
-    private static final String BACK_FOLDER_PATTERN = "yyyy-MM-dd-HHmm";
+    private static final String BACK_FOLDER_PATTERN = "yyMMdd-HHmm";
 
     private static final String BACKUP_ROOT = "backup";
 
@@ -84,5 +84,4 @@ public class PrepareInstallationBackupAction implements PanelAction
         }
         return result;
     }
-
 }