build(deps-dev): bump autoprefixer from 10.5.4 to 10.5.5 in /docs (#7365)

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 10.5.4 to 10.5.5.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/main/CHANGELOG.md)
- [Commits](postcss/autoprefixer@10.5.4...10.5.5)

---
updated-dependencies:
- dependency-name: autoprefixer
  dependency-version: 10.5.5
  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>

Author: dependabot[bot]

docs/package-lock.json

@@ -17,7 +17,7 @@
   },
   "homepage": "https://github.com/pipe-cd/pipecd#readme",
   "devDependencies": {
-    "autoprefixer": "^10.5.4",
+    "autoprefixer": "^10.6.1",
     "postcss": "^8.5.28",
     "postcss-cli": "^11.0.1"
   }