Broken link under querying collections docs

On the [Querying Collections in AngularFirestore](https://github.com/angular/angularfire/blob/master/docs/compat/firestore/querying-collections.md) section, Firestore query API link is giving a 404 error.

Open docs/compat/firestore/querying-collections.md and inspect the Firestore query API link in the “Querying Collections in AngularFirestore” section. Replace the 404 destination with the correct API documentation link, then verify that the link resolves and the documentation still renders correctly.

Written by the indexing model from the issue text.