chore: Update copyright notices

Update copyright notices to comply to GPLv3 and change NewPipe to NewPipe Extractor on some notices that were not updated.

[x] I carefully read the contribution guidelines and agree to them.
[x] I have tested the API against NewPipe.
[ ] I agree to create a pull request for NewPipe as soon as possible to make it compatible with the changed API.

ShareASmile / NewPipeExtractor