Remove incorrect exception expectations from DELETE tests with derived tables

[Copilot]

Tests were expecting MySQL error 1093 for DELETE statements with self-referencing subqueries, but EF Core's query generation using derived tables within EXISTS clauses bypasses this limitation on both MySQL and MariaDB.

Query pattern that works:

DELETE `o` FROM `Order Details` AS `o`
WHERE EXISTS (
    SELECT 1 FROM (
        SELECT `o0`.`OrderID`, `o0`.`ProductID`
        FROM `Order Details` AS `o0`
        WHERE `o0`.`OrderID` < 10300
        LIMIT @p
    ) AS `o1`  -- Derived table materializes result, avoiding error 1093
    WHERE (`o1`.`OrderID` = `o`.`OrderID`) AND (`o1`.`ProductID` = `o`.`ProductID`))

Changes:

• Removed conditional Assert.ThrowsAsync<MySqlException> blocks from 7 test methods
• Tests now execute normally on both MySQL 8.0.40+ and MariaDB 11.6.2+
• Affected tests:
  • Delete_Where_Take
  • Delete_Where_Skip
  • Delete_Where_Skip_Take
  • Delete_Where_OrderBy_Skip
  • Delete_Where_OrderBy_Take
  • Delete_Where_OrderBy_Skip_Take
  • Delete_Where_Skip_Take_Skip_Take_causing_subquery

Note: Direct self-references without derived tables still correctly fail with error 1093 (e.g., Delete_Where_OrderBy test correctly expects exception for queries lacking the derived table wrapper).

Original prompt

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This section details on the original issue you should resolve

<issue_title>Assert.Throws() Failure: No exception was thrown</issue_title>
<issue_description> Failed Pomelo.EntityFrameworkCore.MySql.FunctionalTests.BulkUpdates.NorthwindBulkUpdatesMySqlTest.Delete_Where_Take(async: False) [58 ms]
Error Message:
Assert.Throws() Failure: No exception was thrown
Expected: typeof(MySqlConnector.MySqlException)
Stack Trace:
at Pomelo.EntityFrameworkCore.MySql.FunctionalTests.BulkUpdates.NorthwindBulkUpdatesMySqlTest.Delete_Where_Take(Boolean async) in /home/runner/work/Pomelo.EntityFrameworkCore.MySql/Pomelo.EntityFrameworkCore.MySql/test/EFCore.MySql.FunctionalTests/BulkUpdates/NorthwindBulkUpdatesMySqlTest.cs:line 320
--- End of stack trace from previous location ---

Failed Pomelo.EntityFrameworkCore.MySql.FunctionalTests.BulkUpdates.NorthwindBulkUpdatesMySqlTest.Delete_Where_Take(async: True) [26 ms]
Error Message:
Assert.Throws() Failure: No exception was thrown
Expected: typeof(MySqlConnector.MySqlException)
Stack Trace:
at Pomelo.EntityFrameworkCore.MySql.FunctionalTests.BulkUpdates.NorthwindBulkUpdatesMySqlTest.Delete_Where_Take(Boolean async) in /home/runner/work/Pomelo.EntityFrameworkCore.MySql/Pomelo.EntityFrameworkCore.MySql/test/EFCore.MySql.FunctionalTests/BulkUpdates/NorthwindBulkUpdatesMySqlTest.cs:line 320
--- End of stack trace from previous location ---</issue_description>

<agent_instructions>restore, build, ensure mysql 8.0.40 is running, run test, fix code, retest before committing also against mariadb 11.6.2.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Assert.Throws() Failure: No exception was thrown #225

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