Fix incorrect exception type in DataTableReader.GetOrdinal documentation

[Copilot]

The documentation for DataTableReader.GetOrdinal(string name) incorrectly stated in the Remarks section that an IndexOutOfRangeException is thrown when a column name is not found. This contradicted both the method's Exceptions section and the supporting code examples, which correctly indicate that an ArgumentException is thrown.

Changes Made

• Updated line 1501 in xml/System.Data/DataTableReader.xml to change IndexOutOfRangeException to ArgumentException in the remarks section

Verification

The fix aligns the documentation with:

1. The method's own Exceptions section which lists ArgumentException for invalid column names
2. The code example in the snippets which catches ArgumentException when calling GetOrdinal
3. The actual behavior of the method as implemented

This is a minimal documentation-only change that resolves the inconsistency without affecting any functionality.

Fixes #11442.

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[jeffhandley]

Verified that the implementation results in an ArgumentException as reported.

https://github.com/dotnet/runtime/blob/39a31f082e77fb8893016c30c0858f0e5f8c89ea/src/libraries/System.Data.Common/src/System/Data/DataTableReader.cs#L634

https://github.com/dotnet/runtime/blob/39a31f082e77fb8893016c30c0858f0e5f8c89ea/src/libraries/System.Data.Common/src/System/Data/DataException.cs#L401

https://github.com/dotnet/runtime/blob/39a31f082e77fb8893016c30c0858f0e5f8c89ea/src/libraries/System.Data.Common/src/System/Data/DataException.cs#L338