Fix integration tests for TFWav2Vec2 and TFHubert

[anton-l]

Issue
Errors for integration tests on TFWav2Vec2 and TFHubert

E           ValueError: When setting ``truncation=True``, make sure that ``max_length`` is defined and ``padding='max_length'

CI logs: https://github.com/huggingface/transformers/runs/3539314355?check_suite_focus=true

Solution
Remove truncation=True from feature extractors since the logic changed recently #12804
Also some other small fixes because the tests now reach those lines 🙂

[LysandreJik]

Thank you @anton-l!