update the maximum size of transaction (pingcap#8991)

Author: ran-huang

transaction-overview.md

@@ -293,7 +293,7 @@ Due to the limitations of the underlying storage engine, TiDB requires a single
 
 TiDB supports both optimistic and pessimistic transactions, and optimistic transactions are the basis for pessimistic transactions. Because optimistic transactions first cache the changes in private memory, TiDB limits the size of a single transaction.
 
-By default, TiDB sets the total size of a single transaction to no more than 100 MB. You can modify this default value via `txn-total-size-limit` in the configuration file. The maximum value of `txn-total-size-limit` is 10 GB. The individual transaction size limit also depends on the size of remaining memory available in the server. This is because when a transaction is executed, the memory usage of the TiDB process is scaled up comparing with the transaction size, up to two to three times or more of the transaction size.
+By default, TiDB sets the total size of a single transaction to no more than 100 MB. You can modify this default value via `txn-total-size-limit` in the configuration file. The maximum value of `txn-total-size-limit` is 1 TB. The individual transaction size limit also depends on the size of remaining memory available in the server. This is because when a transaction is executed, the memory usage of the TiDB process is scaled up comparing with the transaction size, up to two to three times or more of the transaction size.
 
 TiDB previously limited the total number of key-value pairs for a single transaction to 300,000. This restriction was removed in TiDB v4.0.