Possible memory leak using firestore

Hi,

I suspect there is a memory leak when using firestore nodejs lib. I have an application running in GCP cloud runs, and memory never stops growing until it cannot allocate more than the 4GB I have reserved.

I have reduced my app to the example below (where I have redacted enterprise info). I simply get items, not even using them, and memory would never be properly cleared by the GC.

You can run the below script using the first argument as a number to produce more calls, here is the data I gathered looking at the process memory usage with `ps`:

```
// 10000 calls > 259 MB
// 1000 calls > 181 MB
// 100 calls > 151 MB
// 0 calls > 95 MB
```

*To be thorough, I ran a similar sample using a mongodb database, and memory is properlly GC'd and goes back to around 150MB whatever the number of samples.*

My code might have issues, in which case I would be happy to know how to fix it 👍

#### Environment details

- OS: Ubuntu 24.04.3 LTS
- Node.js version: v22.17.1
- npm version: 10.9.2
- `@google-cloud/firestore` version: 7.11.6 /

#### Steps to reproduce

Execute the following code, and look at the memory of the process:

```shell
node --exmerimental-strip-types filename.ts 1
node --exmerimental-strip-types filename.ts 10
node --exmerimental-strip-types filename.ts 100
node --exmerimental-strip-types filename.ts 1000
```

```ts
import { Firestore } from "@google-cloud/firestore";

const iteration = Number(process.argv[2]);

console.log(`iterating ${iteration}`);

for (let i = 0; i < iteration; i++) {

const firestore = new Firestore({
projectId: "my_project_id",
});

await Promise.all(
Array.from(Array(100).keys()).map(async () => {
await firestore
.collection("myCollection")
.where("name", "==", "my name")
.limit(1)
.get();
}),
);
await firestore.terminate();

console.log(`done ${(i + 1) * 100}`);
}

console.log("waiting...");

setTimeout(() => console.log("done"), 1000000);
```