fixes #2988 "Update clean-css dependency in pug-filters" (#2989)

Author: callmeaponte

packages/pug-filters/package.json

@@ -6,7 +6,7 @@
     "pug"
   ],
   "dependencies": {
-    "clean-css": "^3.3.0",
+    "clean-css": "^4.1.11",
     "constantinople": "^3.0.1",
     "jstransformer": "1.0.0",
     "pug-error": "^1.3.2",