deps: update firebase-functions requirement

Updates the requirements on [firebase-functions](https://github.com/firebase/firebase-functions-python) to permit the latest version.

Updates `firebase-functions` to 0.4.2
- [Release notes](https://github.com/firebase/firebase-functions-python/releases)
- [Commits](firebase/firebase-functions-python@0.1.0...0.4.2)

---
updated-dependencies:
- dependency-name: firebase-functions
  dependency-type: direct:production
  dependency-group: safe-dependencies
...

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

functions/requirements.txt

@@ -1,2 +1,2 @@
-firebase_functions~=0.1.0
+firebase_functions~=0.4.2
 arcgis==2.*