mypy fixes for Spotify provider (#2436)

mypy fixes for Spotify provider (#2436)

* mypy fixes for Spotify provider

* Update pyproject.toml

* Update music_assistant/providers/spotify/provider.py

Co-authored-by: Marcel van der Veldt <m.vanderveldt@outlook.com>
* Update music_assistant/providers/spotify/provider.py

Co-authored-by: Marcel van der Veldt <m.vanderveldt@outlook.com>
* Apply suggestion from @marcelveldt

Co-authored-by: Marcel van der Veldt <m.vanderveldt@outlook.com>
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Co-authored-by: Marcel van der Veldt <m.vanderveldt@outlook.com>
Co-authored-by: Maxim Raznatovski <nda.mr43@gmail.com>