stash: Remove old versions

[ParkMyCar]

This PR removes versions of the Stash that were introduced in v0.67 or older, the current production release is v0.71.

Motivation

Reduces build and test times of the mz_stash crate.

Checklist

• This PR has adequate test coverage / QA involvement has been duly considered.
• This PR has an associated up-to-date design doc, is a design doc (template), or is sufficiently small to not require a design.
• If this PR evolves an existing $T ⇔ Proto$T mapping (possibly in a backwards-incompatible way), then it is tagged with a T-proto label.
• If this PR will require changes to cloud orchestration or tests, there is a companion cloud PR to account for those changes that is tagged with the release-blocker label (example).
• This PR includes the following user-facing behavior changes:
  • N/a

[maddyblue]

Wait I thought that removing old versions required changing the initial stash population too?

[ParkMyCar]

required changing the initial stash population too?

Do you mean the initialization flow? If so, initializing a new Stash/Catalog intentionally uses the latest proto objects, and does not use any old version, which makes a delete like this safe.

[maddyblue]

Ah I did not realize that stash opening does either init or upgrade. I would have pushed we do this PR much earlier if I had known that since there's no real choices to be made. Neat!