Bump postcss from 8.5.3 to 8.5.4 in /src/Elastic.Markdown (#1333)

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.3 to 8.5.4.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.3...8.5.4)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.4
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

src/Elastic.Markdown/package-lock.json

@@ -33,7 +33,7 @@
     "eslint": "9.28.0",
     "globals": "16.1.0",
     "parcel": "2.15.2",
-    "postcss": "8.5.3",
+    "postcss": "8.5.4",
     "postcss-import": "16.1.0",
     "prettier": "3.5.3",
     "prettier-plugin-tailwindcss": "0.6.12",