FirebaseError object endpoints[testme].availableMemoryMb failed validation

### [REQUIRED] Version info

**node:** v16.13.1

**firebase-functions:** 4.0.0-rc.0 (also reproduced with 3.24.1)

**firebase-tools:** N/A (in yarn.lock)

**firebase-admin:** 11.1.0

### [REQUIRED] Test case

```
const admin = require('firebase-admin');
const functions = require("firebase-functions");

admin.initializeApp();

exports.testme = functions.firestore.document('/users/{ts}')
.onUpdate((snap, context) => {
functions.logger.debug("This is a test");
});
```
### [REQUIRED] Steps to reproduce

```
firebase deploy --only functions:testme
```

### [REQUIRED] Expected behavior

The deployment completes successfully, as it always happened on this codebase for the last 6 months (and as far as I can recall, while working with Firebase Functions)

### [REQUIRED] Actual behavior

```
=== Deploying to 'fenix-app-39599'...

i deploying functions
i functions: ensuring required API cloudfunctions.googleapis.com is enabled...
i functions: ensuring required API cloudbuild.googleapis.com is enabled...
i artifactregistry: ensuring required API artifactregistry.googleapis.com is enabled...
✔ artifactregistry: required API artifactregistry.googleapis.com is enabled
✔ functions: required API cloudbuild.googleapis.com is enabled
✔ functions: required API cloudfunctions.googleapis.com is enabled
i functions: preparing codebase default for deployment
Error: Failed to parse build specification:
- FirebaseError object endpoints[testme].availableMemoryMb failed validation

Having trouble? Try firebase [command] --help
```

### Were you able to successfully deploy your functions?

See above.