removed checkpoint from prediction

[dennisbader]

Fixes #820.

Summary

• Removed checkpoint from prediction. We already load the model state when calling load_from_checkpoint(), which is why we can remove it from predict()
• Updated docs for loading methods as suggested in Model can't find encoding_available variable [BUG] #814.

[codecov-commenter]

Codecov Report

Merging #821 (728789c) into master (cbe49bf) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #821      +/-   ##
==========================================
- Coverage   91.33%   91.33%   -0.01%     
==========================================
  Files          69       69              
  Lines        6869     6867       -2     
==========================================
- Hits         6274     6272       -2     
  Misses        595      595              

Impacted Files	Coverage Δ
...arts/models/forecasting/torch_forecasting_model.py	89.10% <100.00%> (-0.05%)	⬇️

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[hrzn]

Thanks!