Update dependency postcss to v8.4.8

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
postcss (source)	8.4.7 -> 8.4.8

---

Release Notes

postcss/postcss

### [`v8.4.8`](https://togithub.com/postcss/postcss/blob/HEAD/CHANGELOG.md#​848) [Compare Source](https://togithub.com/postcss/postcss/compare/8.4.7...8.4.8) - Fixed end position in empty Custom Properties.

---

Configuration

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

🚦 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, click this checkbox.

---

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