[Messaging] sendEachForMulticast with a lot of tokens throws error

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### [REQUIRED] Step 2: Describe your environment

* Operating System version: Docker version 28.0.1, build 068a01e (image is: oven/bun:1.2.12-alpine)
* Firebase SDK version: 13.4.0
* Firebase Product: messaging
* Node.js version: v20.18.0
* NPM version: 10.8.2

### [REQUIRED] Step 3: Describe the problem

#### Steps to reproduce:

When using Http/2 with `sendEachForMulticast` will throw an error (`Error while making requests: GOAWAY - exceeded_max_concurrent_streams, Error code: 1`) when sending with a lot fcm tokens (lowest that i have tested that got rejected is 214)

if legacy http transport is enabled, this issue does not occur.

best guess why this happens is the fact that it sends a request for every token, therefore sending up to 500 requests at once which is too many for the http/2 implemenation of it.

#### Relevant Code:

```ts
const app = admin.initializeApp();
const messaging = app.messaging();

const tokens = []; // List of a lot of FCM tokens

try {
const result = await messaging.sendEachForMulticast({ tokens });
} catch (err) {
console.error(err);
}
```