chore(deps): update dependency c8 to v9 (#343)

Author: renovate-bot

core/promisify/package.json

@@ -34,7 +34,7 @@
     "@types/mocha": "^9.0.0",
     "@types/node": "^20.4.8",
     "@types/sinon": "^10.0.0",
-    "c8": "^8.0.1",
+    "c8": "^9.0.0",
     "chai": "^4.2.0",
     "codecov": "^3.0.4",
     "gts": "^5.0.0",