1.31 version nightly

[ehuss]

I noticed the version of nightly is still 1.30, and I was wondering if updating that is waiting for something? Just slightly confusing, not critical to me.

[Mark-Simulacrum]

I think we haven't bumped the beta compiler yet, I'll go ahead and make that PR soon.

[cuviper]

I already started on this, so I'll send a PR in a moment.

[leonardo-m]

Why isn't Nightly versions bumped automatically when there's a major point release?

[cuviper]

The raw version could simply be bumped as soon as beta is branched from it, but then bumping the bootstrap compiler needs to update stage0 conditionals.