Update dependency mocha to v6.2.3

Author: renovate-bot

package-lock.json

@@ -35,7 +35,7 @@
     "coffee-script": "1.12.7",
     "eslint": "6.8.0",
     "istanbul": "0.4.5",
-    "mocha": "6.2.2",
+    "mocha": "6.2.3",
     "opener": "1.5.1",
     "semantic-release": "15.14.0",
     "sinon": "7.5.0"