feat: upgrade mocha from 9.2.2 to 10.5.2

Snyk has created this PR to upgrade mocha from 9.2.2 to 10.5.2.

See this package in npm:
mocha

See this project in Snyk:
https://app.snyk.io/org/cachiman/project/cbaec002-669a-43f1-9f6b-f9b981d5b44a?utm_source=github-cloud-app&utm_medium=referral&page=upgrade-pr

packages/google-cloud-eventarc/package.json

@@ -59,7 +59,7 @@
     "jsdoc-region-tag": "^3.0.0",
     "linkinator": "4.1.2",
     "long": "^5.2.3",
-    "mocha": "^9.2.2",
+    "mocha": "^10.5.2",
     "pack-n-play": "^2.0.0",
     "sinon": "^17.0.0",
     "typescript": "^5.1.6"