Update dependency prettier to ~2.6.0 (postcss#431)

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

Author: renovate[bot]

package.json

@@ -39,7 +39,7 @@
     "eslint-config-problems": "6.0.0",
     "postcss": "^8.0.4",
     "postcss-import": "^14.0.0",
-    "prettier": "~2.5.0",
+    "prettier": "~2.6.0",
     "sugarss": "^4.0.0",
     "uuid": "^8.0.0"
   },