Review NUnit1030

[atifaziz]

In PR #1023, updating the NUnit.Analyzers to version 3.8.0 introduced NUnit1030 warnings/errors:

A:\MoreLINQ\main\MoreLinq.Test\NullArgumentTest.cs(33,31,33,58): error NUnit1030: The TestCaseSource provides type 'NUnit.Framework.Interfaces.ITestCaseData', but the Test method expects type 'System.Action' for parameter 'testCase' (https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit1030.md)
A:\MoreLINQ\main\MoreLinq.Test\NullArgumentTest.cs(37,31,37,60): error NUnit1030: The TestCaseSource provides type 'NUnit.Framework.Interfaces.ITestCaseData', but the Test method expects type 'System.Action' for parameter 'testCase' (https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit1030.md)
A:\MoreLINQ\main\MoreLinq.Test\ReturnTest.cs(151,25,151,51): error NUnit1030: The TestCaseSource provides type 'NUnit.Framework.Interfaces.ITestCaseData', but the Test method expects type 'System.Action' for parameter 'unsupportedAction' (https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit1030.md)

Since all tests pass regardless, the severity of NUnit1030 was demoted to suggestion:

MoreLINQ/MoreLinq.Test/.editorconfig

Lines 41 to 42 in 91d3996

	# NUnit1030: The type of parameter provided by the TestCaseSource does not match the type of the parameter in the Test method
	dotnet_diagnostic.NUnit1030.severity = suggestion

It should be reviewed and ideally restored to a warning.