Update dependency mocha to v8

Author: renovate-bot

package.json

@@ -13,7 +13,7 @@
     "eslint": "^7.0.0",
     "lerna": "^3.4.0",
     "manual-git-changelog": "^1.0.1",
-    "mocha": "^7.0.0",
+    "mocha": "^8.0.0",
     "nyc": "^15.0.0",
     "pre-commit": "^1.1.3",
     "sinon": "^1.17.4",