Update rand dependency

[dmitrmax]

Version of rand before 0.9.0 conflict with edition 2024 as they have Rng::gen() method - gen now is reserved keyword.

[Kixunil]

That's not really a big deal since editions are prepared for these kinds of things but yes, let's upgrade the version anyway.

[dmitrmax]

Any chances to see a new release soon?

[apoelstra]

I'd really like to get #716 in first.