Docs on version 4.0 but not available for 4.0

Not included in the dotnet FW, nuget package requires dotnet FW >= 4.6 for all available versions of the package (4.0.0 to 5.0.0).

So I would have expected all the the docs pages on the this namespace to redirect me to the newest FW version docs and display a notice at the top that it is not available - as is done on other pages that are not available in older versions.

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#### Document Details

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* ID: c6011ea7-5a8b-f930-e8df-667eb3d292c9
* Version Independent ID: 8c62f36b-e437-f806-4652-fbf159779dfe
* Content: [Package Class (System.IO.Packaging)](https://docs.microsoft.com/en-us/dotnet/api/system.io.packaging.package?view=netframework-4.0)
* Content Source: [xml/System.IO.Packaging/Package.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.IO.Packaging/Package.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**