update rand

I can't compile to wasm due to another version of getrandom mixing it up. please update rand!

https://rust-random.github.io/book/update-0.9.html
https://github.com/rust-random/rand/blob/master/CHANGELOG.md

Other older dependencies
https://github.com/starkat99/half-rs/pull/123
https://github.com/briansmith/ring/issues/2341

Start with the linked rand 0.9 update guide and changelog, then inspect Candle's dependency declarations and wasm build path for rand and getrandom versions. Review the linked half-rs and ring references for related constraints. Done means Candle compiles to wasm without conflicting getrandom versions.

Written by the indexing model from the issue text.