docs: add sub-table name by rule note (#17160)

docs/en/20-third-party/05-collectd.md

@@ -72,3 +72,7 @@ taos> select * from collectd.memory_value limit 10;
 Query OK, 10 row(s) in set (0.010348s)
 ```
 
+:::note
+
+- TDengine will automatically create unique IDs for sub-table names by the rule.
+:::

docs/zh/20-third-party/05-collectd.md

@@ -72,3 +72,7 @@ taos> select * from collectd.memory_value limit 10;
 Query OK, 10 row(s) in set (0.010348s)
 ```
 
+:::note
+
+- TDengine 默认生成的子表名是根据规则生成的唯一 ID 值。
+:::