test: cast Assert.DoesNotThrow / Throws delegates to (Action) for NUnit 4

NUnit 4's Assert.DoesNotThrow / Assert.Throws<T> resolve delegate arguments
against multiple overloads (Action, TestDelegate, AsyncTestDelegate). A bare
() => lambda triggers CS0121 overload ambiguity once TrakHound#239 lands the NUnit 4
upgrade. The (Action) cast disambiguates unambiguously in both NUnit 3 and 4,
so the wrap is safe to land on this branch before TrakHound#239 merges.

Fixes cross-PR bug class discovered on integration/up-to-pr-249 build (158
errors, 112 CS0121 across 9 test files on 7 PRs). Per-PR fix — each affected
PR wraps its own new test sites so the class stays clean across the train.

Author: ottobolyos

tests/MTConnect.NET-Common-Tests/V2_6_V2_7/V2_7DataItemTypeTests.cs

@@ -49,7 +49,7 @@ public void V2_7_DataItem_constructs_with_correct_metadata(
             // surfaces as a clear NUnit failure with the offending type name
             // rather than a bare MissingMethodException.
             object? instance = null;
-            Assert.DoesNotThrow(() => instance = Activator.CreateInstance(dataItemType),
+            Assert.DoesNotThrow((Action)(() => instance = Activator.CreateInstance(dataItemType)),
                 $"{dataItemType.Name} should have a public parameterless constructor");
             Assert.That(instance, Is.Not.Null);
             Assert.That(instance, Is.InstanceOf<DataItem>());