Update system-variables.md

fix 404 (hard link).

system-variables.md

@@ -1595,7 +1595,7 @@ mysql> SELECT job_info FROM mysql.analyze_jobs ORDER BY end_time DESC LIMIT 1;
 - This variable is used to specify the cloud storage URI to enable [Global Sort](/tidb-global-sort.md). After enabling the [distributed execution framework](/tidb-distributed-execution-framework.md), you can use the Global Sort feature by configuring the URI and pointing it to an appropriate cloud storage path with the necessary permissions to access the storage. For more details, see [URI format](https://docs.pingcap.com/tidb/stable/backup-and-restore-storages#uri-format).
 - The following statements can use the Global Sort feature.
     - The [`ADD INDEX`](/sql-statements/sql-statement-add-index.md) statement.
-    - The [`IMPORT INTO`](https://docs.pingcap.com/tidb/stable/sql-statement-import-into) statement for import jobs of TiDB Self-Hosted. For TiDB Cloud, the `IMPORT INTO` statement is not applicable.
+    - The [`IMPORT INTO`](/sql-statements/sql-statement-import-into.md) statement for import jobs of TiDB Self-Hosted. For TiDB Cloud, the `IMPORT INTO` statement is not applicable.
 
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