ci: setup rust in the deploy step

[marcoieni]

#2425 failed because it doesn't use the latest stable version.

With this PR, we make sure the Deploy step uses the same Rust version as the other CI jobs.

[github-actions]

Dry-run check results

[WARN  rust_team::sync] sync-team is running in dry mode, no changes will be applied.
[INFO  rust_team::sync] synchronizing crates-io
[INFO  rust_team::sync] synchronizing github
[INFO  rust_team::sync] 💻 Repo Diffs:
    📝 Editing repo 'rust-lang/rust':
      Rulesets:
          Updating '*/**/*'
            Dismiss stale reviews on push: deleting `false`
            Require code owner review: deleting `false`
            Require last push approval: deleting `false`
            Require pull requests: true => false
            Require review thread resolution: deleting `false`
            Required approvals: deleting `1`