Correct seek signature to return int instead of bytes

[maksdamir]

Current examples suggest seek api on file-like objects should return bytes, while actual usage always expects int instead.

For example: https://docs.python.org/3/library/io.html#io.IOBase.seek

seek(offset, whence=os.SEEK_SET, /)
Change the stream position to the given byte offset, interpreted relative to the position indicated by whence, and return the new absolute position.

[facebook-github-bot]

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[Dan-Flores]

Good catch, thanks for the PR @maksdamir!

[scotts]

@maksdamir, wow, great catch, thank you!