Documention incorrect for edge cases

The method has different return value for edge between .NET Framework and .NET Core
For instance :
Pow(double.NaN, 0) will return 1 in .Net Core and double.NaN in .NetFramework

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#### Document Details

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* ID: 1877175b-aef3-5358-ac70-7ea02fd96dea
* Version Independent ID: 4df66b7a-6548-866c-afab-19e9a3140342
* Content: [Math.Pow(Double, Double) Method (System)](https://docs.microsoft.com/en-us/dotnet/api/system.math.pow?view=netcore-2.2#System_Math_Pow_System_Double_System_Double_)
* Content Source: [xml/System/Math.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System/Math.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**