Update mocha to version 6.1.4

Author: depfu[bot]

package.json

@@ -38,7 +38,7 @@
     "eslint-plugin-prettier": "^3.0.0",
     "lodash.escape": "^4.0.1",
     "lodash.unescape": "^4.0.1",
-    "mocha": "^5.2.0",
+    "mocha": "^6.1.4",
     "offline-github-changelog": "^1.2.0",
     "prettier": "^1.15.3",
     "serve": "^11.0.0",