9.x: Inconsistent to define 'Edm.Untyped' property or 'Collection(Edm.Untyped)' property

[xuzhg]

Describe the bug

    this.serverEntityType.AddStructuralProperty("Infos",
        new EdmCollectionTypeReference(new EdmCollectionType(EdmCoreModel.Instance.GetUntyped())));

vs

   this.serverEntityType.AddStructuralProperty("Infos",
        new EdmCollectionTypeReference(new EdmCollectionType(EdmUntypedStructuredTypeReference.NullableTypeReference)));

Both can get the following property:

 <Property Name="Info" Type="Collection(Edm.Untyped)" />

1. Which one should take?
2. We should only keep one?

Assemblies affected

Which assemblies and versions are known to be affected e.g. Microsoft.OData.Core 9.x

Steps to Reproduce

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Expected behaviour

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Actual behaviour

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Additional details

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