Move SameSite 3.0 breaking change to list in .NET Core docs (#15794)

Author: scottaddie

aspnetcore/migration/22-to-30.md

@@ -1233,7 +1233,6 @@ Review breaking changes:
 * [Complete list of breaking changes in the ASP.NET Core 3.0 release](https://github.com/aspnet/Announcements/issues?page=1&q=is%3Aissue+is%3Aopen+label%3A%22Breaking+change%22+label%3A3.0.0)
 * [Breaking API changes in Antiforgery, CORS, Diagnostics, MVC, and Routing](https://github.com/aspnet/Announcements/issues/387). This list includes breaking changes for compatibility switches.
 * For a summary of 2.2-to-3.0 breaking changes across .NET Core, ASP.NET Core, and Entity Framework Core, see [Breaking changes for migration from version 2.2 to 3.0](/dotnet/core/compatibility/2.2-3.0).
-* [Some Cookie SameSite defaults changed to None (aspnet/Announcements #348)](https://github.com/aspnet/Announcements/issues/348).
 
 ## .NET Core 3.0 on Azure App Service