[BUG] in sample: fcm functions

### Which sample has a bug?

**Sample name or URL where you found the bug**

firebase fcm functions

### How to reproduce the issue

**Failing Function code used (if you modified the sample)**

**Steps to set up and reproduce**

The provided examples make use of the old sendToDevice method. This uses the old legacy API, that needs to be enabled separately and it’s not recommended to use.

### Debug output

**Errors in the
[console logs](https://console.firebase.google.com/project/_/functions/logs?search=&severity=DEBUG)**

**Screenshots**

### Expected behavior

Use the newest methods instead

### Actual behavior