glossary: fix descrption about isolation (#18809) (#18812)

glossary.md

@@ -15,7 +15,7 @@ ACID refers to the four key properties of a transaction: atomicity, consistency,
 
 - **Consistency** means that transactions always bring the database from one consistent state to another. In TiDB, data consistency is ensured before writing data to the memory.
 
-- **Isolation** means that a transaction in process is invisible to other transactions until it completes. This allows concurrent transactions to read and write data without sacrificing consistency. TiDB currently supports the isolation level of `REPEATABLE READ`.
+- **Isolation** means that a transaction in process is invisible to other transactions until it completes. This allows concurrent transactions to read and write data without sacrificing consistency. For more information, see [TiDB transaction isolation levels](/transaction-isolation-levels.md#tidb-transaction-isolation-levels).
 
 - **Durability** means that once a transaction is committed, it remains committed even in the event of a system failure. TiKV uses persistent storage to ensure durability.