Bump autoprefixer from 9.8.6 to 9.8.7 (#16785)

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 9.8.6 to 9.8.7.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/9.8.7/CHANGELOG.md)
- [Commits](https://github.com/postcss/autoprefixer/compare/9.8.6...9.8.7)

---
updated-dependencies:
- dependency-name: autoprefixer
  dependency-type: direct:production
  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>

package.json

@@ -72,7 +72,7 @@
     "@rails/ujs": "^6.1.4",
     "array-includes": "^3.1.3",
     "arrow-key-navigation": "^1.2.0",
-    "autoprefixer": "^9.8.6",
+    "autoprefixer": "^9.8.7",
     "axios": "^0.21.4",
     "babel-loader": "^8.2.2",
     "babel-plugin-lodash": "^3.3.4",