security: bump autoprefixer from 9.8.6 to 9.8.8 in /website (#765)

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 9.8.6 to 9.8.8.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/9.8.8/CHANGELOG.md)
- [Commits](postcss/autoprefixer@9.8.6...9.8.8)

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

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

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

website/package.json

@@ -18,7 +18,7 @@
   "homepage": "https://github.com/google/docsy-example#readme",
   "dependencies": {},
   "devDependencies": {
-    "autoprefixer": "^9.8.6",
+    "autoprefixer": "^9.8.8",
     "postcss-cli": "^7.1.2"
   }
 }