Bump chai from 4.2.0 to 4.3.6 in /functions

Bumps [chai](https://github.com/chaijs/chai) from 4.2.0 to 4.3.6.
- [Release notes](https://github.com/chaijs/chai/releases)
- [Changelog](https://github.com/chaijs/chai/blob/4.x.x/History.md)
- [Commits](chaijs/chai@4.2.0...v4.3.6)

---
updated-dependencies:
- dependency-name: chai
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

functions/package-lock.json

@@ -27,7 +27,7 @@
     "@types/chai": "^4.2.12",
     "@types/chai-as-promised": "^7.1.3",
     "@types/mocha": "^8.0.4",
-    "chai": "^4.2.0",
+    "chai": "^4.3.6",
     "chai-as-promised": "^7.1.1",
     "firebase-functions-test": "^0.2.3",
     "mocha": "^8.2.1",