update postcss to patched version (#1408)

Author: aliciapaz

package.json

@@ -60,7 +60,7 @@
     "fs-extra": "^9.1.0",
     "jest": "^26.6.3",
     "lint-staged": "^10.5.4",
-    "postcss": "^8.2.8",
+    "postcss": "^8.2.15",
     "prettier": "^2.2.1",
     "simple-git-hooks": "^2.0.2",
     "size-limit": "^4.10.1",