chore(deps): Update dependency postcss to v8.4.31 [SECURITY]

Author: renovate[bot]

package-lock.json

@@ -19,7 +19,7 @@
     "gulp-svgmin": "^4.1.0",
     "gulp-uglify": "^3.0.0",
     "plugin-error": "^1.0.1",
-    "postcss": "8.4.17",
+    "postcss": "8.4.31",
     "request": "^2.79.0",
     "request-promise-native": "^1.0.3",
     "sass": "1.55.0"