Bump postcss-preset-env from 6.7.0 to 9.6.0

Bumps [postcss-preset-env](https://github.com/csstools/postcss-plugins/tree/HEAD/plugin-packs/postcss-preset-env) from 6.7.0 to 9.6.0.
- [Changelog](https://github.com/csstools/postcss-plugins/blob/main/plugin-packs/postcss-preset-env/CHANGELOG.md)
- [Commits](https://github.com/csstools/postcss-plugins/commits/HEAD/plugin-packs/postcss-preset-env)

---
updated-dependencies:
- dependency-name: postcss-preset-env
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

package.json

@@ -54,7 +54,7 @@
     "postcss-header": "^3.0.1",
     "postcss-import": "^14.0.2",
     "postcss-prefixer": "^2.1.3",
-    "postcss-preset-env": "^6.7.0",
+    "postcss-preset-env": "^9.6.0",
     "prettier": "^2.7.1"
   },
   "lint-staged": {