chore: bump rust version in ci to 1.73.0

[noot]

Summary

bump rust version in ci to 1.73.0

Background

required for #579; had to bump penumbra deps, which bumped libp2p, which requires rust >=1.73.0

Changes

• bump rust version in ci to 1.73.0

[joroshiba]

We should update the docker images as well probably

[SuperFluffy]

This change and the bump to prost/prost-build 0.12 in #579 is currently blocked on protoc-gen-prost still being on prost 0.11.

[SuperFluffy]

Requesting changes because I think we are actually blocked on this and the changes in #579:

1. I would like to separate wider dependency bumps and feature PRs. This bump to 1.73 is explained by another PR, but ideally the reason for bumping should be tied to that PR.

2. But more importantly: I did prepare a PR bumping penumbra (and celestia) to their latest versions, which would allow us to use prost/prost-build 0.12 and tonic 0.10 (as does #579), but that is currently blocked on protoc-gen-prost still being on prost 0.11 (which we are using through buf).

Point 2. is a problem.

Other than forking protoc-gen-prost the only way to fix this is to move off buf temporarily. I am not sure how feasible it is to fork protoc-gen-prost because it would require us to somehow put the fork on buf and make it available to buf.

[noot]

@SuperFluffy okay, should i merge this PR into my IBC branch for now then? i figured the rust version bump would be separate enough for its own PR but either way is fine with me!

[SuperFluffy]

Closing this in favor of #581 (move away from buf) and #582 (bump all dependencies)

@noot these two should unblock #579