[ISSUE #9945] Use UniqueKey as the TimerDelKey value when no namespace is appended (#9951)

Author: imzs

store/src/main/java/org/apache/rocketmq/store/timer/rocksdb/Timeline.java

@@ -288,7 +288,7 @@ private String extractUniqKey(String deleteKey) throws IllegalArgumentException
             }
             int separatorIndex = deleteKey.indexOf(DELETE_KEY_SPLIT);
             if (separatorIndex == -1) {
-                throw new IllegalArgumentException("Invalid deleteKey format");
+                return deleteKey;
             }
             return deleteKey.substring(separatorIndex + 1);
         }