Document the MySQL bug fixed in #263.

Author: bgrainger

docs/content/tutorials/migrating-from-connector-net.md

@@ -67,3 +67,4 @@ may execute differently with MySqlConnector. To get Connector/NET-compatible beh
 * [#84220](https://bugs.mysql.com/bug.php?id=84220): Cannot call a stored procedure with `.` in its name
 * [#84701](https://bugs.mysql.com/bug.php?id=84701): Can't create a paramter using a 64-bit enum with a value greater than int.MaxValue
 * [#85185](https://bugs.mysql.com/bug.php?id=85185): `ConnectionReset=True` does not preserve connection charset
+* [#86263](https://bugs.mysql.com/bug.php?id=86263): Transaction isolation level affects all transactions in session