Update dependency postcss to v8.5.9 (#19029)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

package.json

@@ -109,7 +109,7 @@
     "parse-json": "8.3.0",
     "picocolors": "1.1.1",
     "please-upgrade-node": "3.2.0",
-    "postcss": "8.5.8",
+    "postcss": "8.5.9",
     "postcss-less": "6.0.0",
     "postcss-media-query-parser": "0.2.3",
     "postcss-scss": "4.0.9",