Bump postcss in /packages/tailwindcss-language-server

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.10 to 8.5.18.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.10...8.5.18)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.18
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

packages/tailwindcss-language-server/package.json

@@ -81,7 +81,7 @@
     "normalize-path": "3.0.0",
     "picomatch": "^4.0.1",
     "pkg-up": "3.1.0",
-    "postcss": "8.5.10",
+    "postcss": "8.5.18",
     "postcss-import": "^16.1.0",
     "postcss-load-config": "3.0.1",
     "postcss-selector-parser": "6.0.2",