Update actions/checkout action to v2.4.0

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	minor	v2.3.5 -> v2.4.0

---

Release Notes

actions/checkout

### [`v2.4.0`](https://togithub.com/actions/checkout/releases/v2.4.0) [Compare Source](https://togithub.com/actions/checkout/compare/v2.3.5...v2.4.0) - Convert SSH URLs like `org-@​github.com:` to `https://github.com/` - [pr](https://togithub.com/actions/checkout/pull/621)

---

Configuration

📅 Schedule: At any time (no schedule defined).

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR is behind base branch, 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, click this checkbox.

---

This PR has been generated by WhiteSource Renovate. View repository job log here.