ObjectSizeTests.cs uses `#if NET462 || NET` but NET462 is not defined

[jafin]

Describe the bug
The test file ObjectSizeTests.cs uses #if NET462 || NET but I don't see NET462 defined. Should it be NET462_OR_GREATER || NET or just NET472 || NET (given net462 isn't a valid compile target for this library) or just remove the conditional entirely?, so it can run on NET472 ?

Open-XML-SDK/test/DocumentFormat.OpenXml.Framework.Tests/ObjectSizeTests.cs

Line 4 in 431ab05

#if NET462 || NET

[rghvgrv]

I would like to work on this and provided the fix - #2151