Update check in BindAsync and Mvc.ApiExplorer test

Author: captainsafia

src/Http/Http.Extensions/src/RequestDelegateFactory.cs

@@ -816,7 +816,7 @@ private static Expression BindParameterFromBindAsync(ParameterInfo parameter, Fa
         {
             // We reference the boundValues array by parameter index here
             var nullability = NullabilityContext.Create(parameter);
-            var isOptional = parameter.HasDefaultValue || nullability.ReadState == NullabilityState.Nullable;
+            var isOptional = IsOptionalParameter(parameter);
 
             // Get the BindAsync method
             var body = TryParseMethodCache.FindBindAsyncMethod(parameter.ParameterType)!;

src/Mvc/Mvc.ApiExplorer/test/EndpointMetadataApiDescriptionProviderTest.cs

@@ -340,7 +340,7 @@ public void AddsMultipleParameters()
             Assert.Equal(typeof(InferredJsonClass), fromBodyParam.Type);
             Assert.Equal(typeof(InferredJsonClass), fromBodyParam.ModelMetadata.ModelType);
             Assert.Equal(BindingSource.Body, fromBodyParam.Source);
-            Assert.True(fromBodyParam.IsRequired);
+            Assert.False(fromBodyParam.IsRequired); // Reference type in oblivious nullability context
         }
 
         [Fact]