chore(deps): update dependency mocha to v8

Author: renovate-bot

package.json

@@ -52,10 +52,10 @@
     "@sourcegraph/eslint-config": "^0.23.0",
     "@sourcegraph/prettierrc": "^3.0.3",
     "@sourcegraph/tsconfig": "^4.0.1",
-    "@types/mocha": "7.0.2",
+    "@types/mocha": "8.2.2",
     "eslint": "^7.28.0",
     "husky": "^3.0.2",
-    "mocha": "^7.2.0",
+    "mocha": "^8.4.0",
     "nyc": "^15.1.0",
     "prettier": "^2.2.1",
     "semantic-release": "^17.0.0",