Fix Python type hints so that mypy passes

[cclauss]

% mypy --exclude "old-onix-bot" --exclude "twitter-borrowbot" --install-types --non-interactive .

Found 66 errors in 22 files (checked 33 source files)

[sbshah97]

Hi I am an old contributor is this something that can be picked up?

[devBitt]

can i work on this as my first contribution

[cclauss]

Pull requests will be reviewed... Please dive in.

[devBitt]

@cclauss can you please give contribution and pr guidelines if there is any

[cclauss]

• https://github.com/internetarchive/openlibrary-bots/blob/master/CONTRIBUTING.md
• https://github.com/internetarchive/openlibrary/blob/master/CONTRIBUTING.md