Consider not using the obsolete ServicePointManager

[jjonescz]

We use it in several places like:

https://github.com/dotnet/roslyn/blob/b1567b7c200461e1df4f3644ec107c494d925c83/src/Features/DiagnosticsTestUtilities/CodeActions/CSharpCodeFixVerifier%602%2BTest.cs#L45

WebRequest, WebClient, and ServicePoint are obsolete since .NET 6. See https://learn.microsoft.com/en-us/dotnet/core/compatibility/networking/6.0/webrequest-deprecated.

So it raises warning https://learn.microsoft.com/en-us/dotnet/fundamentals/syslib-diagnostics/syslib0014.

[CyrusNajmabadi]

This is a roslyn-analyzers type.