Remove dependency on Microsoft.Bcl.TimeProvider for .NET 8+ targets

[filipnavara]

Remove dependency on Microsoft.Bcl.TimeProvider for .NET 8+ targets

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Description

.NET 8+ includes the System.TimeProvider in product assemblies and thus doesn't need the Microsoft.Bcl.TimeProvider OOB package.

Due to authoring error in Microsoft.Bcl.TimeProvider 8.0.1 (dotnet/runtime#109163) the extra reference may cause build errors in scenarios building for Apple platforms or using PublishTrimmed=true.