[v1.0.1] Remove `aiohttp` from extra dependencies

In huggingface_hub v1.0 release, we've removed our dependency on aiohttp to replace it with httpx but we forgot to remove it from the huggingface_hub[inference] extra dependencies in setup.py. This patch release removes it, making the inference extra removed as well.

The internal method _import_aiohttp being unused, it has been removed as well.

• Remove aiohttp dependency by @Wauplin in #3488

Full Changelog: v1.0.0...v1.0.1