fix(deps): update dependency postcss to v7.0.30 (#8288)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

install/package.json

@@ -98,7 +98,7 @@
         "passport-local": "1.0.0",
         "pg": "^8.0.2",
         "pg-cursor": "^2.1.9",
-        "postcss": "7.0.27",
+        "postcss": "7.0.30",
         "postcss-clean": "1.1.0",
         "promise-polyfill": "^8.1.3",
         "prompt": "^1.0.0",