GitLab

Summary:
Currently, the documentation page for `torchaudio.models` have separate sections for model definitions and factory functions.

The relationships between models and factory functions are not immediately clear.

This commit moves the list of factory functions to the list of models.

After:
 - https://output.circle-artifacts.com/output/job/242a9521-7460-4043-895b-9995bf5093b5/artifacts/0/docs/generated/torchaudio.models.Wav2Vec2Model.html

<img width="1171" alt="Screen Shot 2022-12-08 at 8 41 03 PM" src="https://user-images.githubusercontent.com/855818/206603743-74a6e368-c3cf-4b87-b854-518a95893f06.png">

Pull Request resolved: https://github.com/pytorch/audio/pull/2902

Reviewed By: carolineechen

Differential Revision: D41897800

Pulled By: mthrok

fbshipit-source-id: a3c01d28d80e755596a9bc37c951960eb84870b9