Update dependency mocha to v8.3.0

Author: renovate-bot

package.json

@@ -18,7 +18,7 @@
     "eslint": "7.21.0",
     "eslint-plugin-ghost": "2.0.0",
     "mkdirp": "1.0.4",
-    "mocha": "8.2.1",
+    "mocha": "8.3.0",
     "should": "13.2.3",
     "sinon": "9.2.4"
   },