chore(deps): update dependency mocha to v6

Author: renovate-bot

package.json

@@ -121,7 +121,7 @@
     "jsdom": "^11.5.1",
     "jsdom-global": "^3.0.2",
     "lint-staged": "^8.0.4",
-    "mocha": "^5.2.0",
+    "mocha": "^6.0.0",
     "nyc": "^13.1.0",
     "prettier": "^1.15.2",
     "prettier-eslint": "^8.8.2",