Update rust version to 1.77.2

[YJDoc2]

Cross updated its msrv to 1.77.2 in cross-rs/cross@7129d5a , so we need to update ours too, as otherwise CI fails to install cross.

Alternatively we can pin cross version, but this is not a big change, and we would be updating rust version eventually anyways.

[YJDoc2]

Thanks @jprendes !

[jprendes]

I believe an alternative, if we don't want cross to dictate our MSRV would be to do cargo +stable install cross --git https://github.com/cross-rs/cross.

[YJDoc2]

I believe an alternative, if we don't want cross to dictate our MSRV would be to do cargo +stable install cross --git https://github.com/cross-rs/cross.

Yes, I had also considered that, but I felt their msrv update was a jump 64->77, and don't think are frequent, so decided to update our msrv. In case we observe it to be much more frequent, I'll take the suggested approach and pin cross version instead.