OData: "The allowed functions are: allFunctions"

[spaasis]

As discussed in #757

The reason for the behavior is an invalid enum check in https://github.com/microsoft/aspnet-api-versioning/blob/e16b579d240574053ebd8e7ee38c8686beaee174/src/Common.OData.ApiExplorer/AspNet.OData/Builder/DefaultODataQueryOptionDescriptionProvider.cs#L244-L245

The value passed to the block is AllowedFunctions.AllFunctions