collection function has no generic type

### Version info

**Angular:**
12.2.0
**Firebase:**
9.4.0
**AngularFire:**
7.2.0

### How to reproduce these conditions
import {
collection,
} from '@angular/fire/firestore';

### Expected behavior

collection suppose to receive generic type of collection documents interface. as stated in docs

import { collection } from '@angular/fire/firestore';
collection(firestore, 'foo') // CollectionReference

### Actual behavior
generic type is not configured, hence causing a problem on passing to update and doc functions with the generic type of the interface set

.

Start at the @angular/fire/firestore collection entry point and inspect how its return type is declared. Compare it with the documented collection(firestore, 'foo') usage, then check how the resulting type is passed to update and doc. Done means collection accepts the generic type and preserves it for those calls.

由索引模型根据 Issue 内容生成。