Bump postcss from 8.3.9 to 8.4.31 (tailwindlabs#864)

Bumps [postcss](https://github.com/postcss/postcss) from 8.3.9 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.3.9...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

packages/tailwindcss-language-server/package-lock.json

@@ -58,7 +58,7 @@
     "minimatch": "5.1.4",
     "normalize-path": "3.0.0",
     "pkg-up": "3.1.0",
-    "postcss": "8.3.9",
+    "postcss": "8.4.31",
     "postcss-load-config": "3.0.1",
     "postcss-selector-parser": "6.0.2",
     "prettier": "2.3.0",