Remove deprecated code for v0.16.x

[Wauplin]

Not much to remove which is I think a good sign that huggingface_hub is getting more mature :)

• force to use kwargs in ModelHubMixin (instead of passing everything a positional arg)
• not possible anymore to pass model_id as username/repo_name@revision in ModelHubMixin

(+2 type annotations fixes)

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (b347dfd) 82.24% compared to head (226aba8) 82.24%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1492   +/-   ##
=======================================
  Coverage   82.24%   82.24%           
=======================================
  Files          55       55           
  Lines        5913     5904    -9     
=======================================
- Hits         4863     4856    -7     
+ Misses       1050     1048    -2     

Impacted Files	Coverage Δ
src/huggingface_hub/hub_mixin.py	96.00% <ø> (+1.95%)	⬆️
src/huggingface_hub/__init__.py	75.75% <100.00%> (ø)

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[LysandreJik]

Nice ! Cool to see that the API is stabilizing itself 🎉