Update alpine Docker tag to v3.13.2

Created by: renovate[bot]

This PR contains the following updates:

Package	Type	Update	New value	Sourcegraph
alpine	final	patch	3.13.2

---

Renovate configuration

📅 Schedule: "on the 1st through 7th day of the month" 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 WhiteSource Renovate. View repository job log here.