Revert "Bump laravel-mix and laravel-mix-purgecss"

package.json

@@ -25,15 +25,13 @@
     "jquery-minicolors": "^2.1.10",
     "jquery-serializeobject": "^1.0.0",
     "jquery-sparkline": "^2.4.0",
-    "laravel-mix": "^4.0",
-    "laravel-mix-purgecss": "^4.0.0",
+    "laravel-mix": "^2.1",
+    "laravel-mix-purgecss": "^3.0.0",
     "livestamp": "git+https://github.com/mattbradley/livestampjs.git#develop",
     "lodash": "^4.17.11",
     "messenger": "git+https://github.com/HubSpot/messenger.git",
     "moment": "^2.17.1",
     "promise": "^7.3.1",
-    "sass": "^1.15.2",
-    "sass-loader": "7.*",
     "sortablejs": "^1.6.1",
     "sweetalert2": "^6.8.0",
     "vue": "^2.5.17",