Update Rust crate dropshot to 0.16.4

[oxide-renovate]

This PR contains the following updates:

Package	Type	Update	Change
dropshot	workspace.dependencies	patch	0.16.3 -> 0.16.4

---

Configuration

📅 Schedule: Branch creation - "after 8pm,before 6am" in timezone America/Los_Angeles, Automerge - "after 8pm,before 6am" in timezone America/Los_Angeles.

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR has been generated by Renovate Bot.

[oxide-renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: Cargo.lock

Command failed: cargo update --config net.git-fetch-with-cli=true --manifest-path Cargo.toml --package dropshot@0.16.4 --precise 0.16.4
error: failed to acquire package cache lock

Caused by:
  failed to open: /home/ubuntu/.cargo/.package-cache

Caused by:
  failed to create directory `/home/ubuntu/.cargo`

Caused by:
  File exists (os error 17)