Publish a stable 6.0.0 release (without prerelease suffix)

Hi,

Could you please publish a stable 6.0.0 release/tag (without any prerelease suffix like -alpha, -beta, -rc, etc.)?

Right now only prerelease 6.x versions exist, and prereleases are disabled by default in many NuGet setups/CI. This makes upgrading unnecessarily hard for downstream users.

If there are blockers for a stable 6.0.0, could you list them?

Thanks for maintaining Math.NET Numerics!