chore(deps): update postcss-selector-parser (postcss#72)

Author: evilebottnawi

package.json

@@ -47,7 +47,7 @@
   "dependencies": {
     "css-unit-converter": "^1.1.1",
     "postcss": "^7.0.5",
-    "postcss-selector-parser": "^5.0.0-rc.4",
+    "postcss-selector-parser": "^6.0.2",
     "postcss-value-parser": "^3.3.1"
   },
   "ava": {