Remove Microsoft.AspNetCore.SuppressSameSiteNone compat switch

[Tratcher]

#13776 added the compat switch Microsoft.AspNetCore.SuppressSameSiteNone for 3.1 that can now be removed from 5.0. Note the same switch is used in multiple assemblies and they all need to be removed.

Blocked until all the auto-branch merging 2.1->2.2->3.0->3.1->master is done.

https://github.com/aspnet/AspNetCore/search?q=SuppressSameSiteNone&unscoped_q=SuppressSameSiteNone