generated dataconnect.yaml schema has invalid `schemas` property - `fdcwebhooks` experiment enabled

### [REQUIRED] Environment info

**firebase-tools:** v15.22.4
**Firebase SQL Connect for VSCode:** v2.4.1

**Platform:** macOS

### [REQUIRED] Test case

N/A

### [REQUIRED] Steps to reproduce

1. Run `firebase experiments:enable fdcwebhooks`.
- This is enabled by default https://github.com/firebase/firebase-tools/blob/0038038859143bab2a6ac3bd807318d61d7bc942/src/experiments.ts#L202-L206
2. Run `firebase init dataconnect --project demo-project`

firebase init dataconnect --project demo-project

```
$ firebase init dataconnect --project demo-project

######## #### ######## ######## ######## ### ###### ########
## ## ## ## ## ## ## ## ## ## ##
###### ## ######## ###### ######## ######### ###### ######
## ## ## ## ## ## ## ## ## ## ##
## #### ## ## ######## ######## ## ## ###### ########

You're about to initialize a Firebase project in this directory:

/Users/PATH/reports/dataconnect-yaml-schema-1

=== Project Setup

First, let's associate this project directory with a Firebase project.
You can create multiple project aliases by running firebase use --add,

Skipping Firebase project setup because a demo project is provided

=== Dataconnect Setup
⚠ dataconnect: Cannot detect an existing app in the current directory.
✔ Do you want to create an app template? skip
✔ Wrote dataconnect/dataconnect.yaml
✔ Wrote dataconnect/seed_data.gql
✔ Wrote dataconnect/schema/schema.gql
✔ Wrote dataconnect/example/connector.yaml
✔ Wrote dataconnect/example/queries.gql
✔ Wrote dataconnect/example/mutations.gql
i dataconnect: No apps to setup SQL Connect Generated SDKs

=== Agent Skills Setup
If you are using an AI coding agent, Firebase Agent Skills make it an expert at Firebase.
✔ Would you like to install agent skills for Firebase? No

✔ Wrote configuration info to firebase.json
✔ Wrote project information to .firebaserc
✔ Wrote .gitignore

✔ Firebase initialization complete!

To get started:

i Install the SQL Connect VS Code Extensions. You can explore SQL Connect Query on local pgLite and Cloud SQL Postgres Instance.
```

### [REQUIRED] Expected behavior

There should be no errors in the generated `dataconnect.yaml` file

### [REQUIRED] Actual behavior

### Notes

we might need to update the dataconnect-yaml.json to support a `schemas` property in https://github.com/firebase/firebase-tools/blob/0038038859143bab2a6ac3bd807318d61d7bc942/schema/dataconnect-yaml.json#L81-L83