## Description

A long overdue clean-up PR to get rid of the `--legacy-digest` flag on
`sui client upgrade` and `sui move build`. This flag was responsible for
changing the way package digests were calculated, as the algorithm
changed around protocol version 7.

## Test Plan

```
$ cargo simtest
$ env SUI_SKIP_SIMTESTS=1 cargo nextest run
```

---
If your changes are not user-facing and not a breaking change, you can
skip the following section. Otherwise, please indicate what changed, and
then add to the Release Notes section as highlighted during the release
process.

### Type of Change (Check all that apply)

- [ ] protocol change
- [x] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

Removes the `--legacy-digest` flag from the `sui client upgrade` and
`sui move build` CLI commands, as no Sui networks require package
digests to be calculated using the legacy algorithm anymore.