Fix copyright date range generated by Sphinx

It appears as if the copyright on the code was "broken" in a well meaning attempt to make the date auto updating.
Unfortunately this isn't how copyright works as recognized by the US Patent and Trademark Office nor the World Intellectual Property Organization (WIPO). You want to specify the time that the copyright _begins_ not the current date.

For more information check out:
- https://www.nolo.com/legal-encyclopedia/when-do-you-need-copyright-notice-websites-and-where-do-you-place-it.html
- https://stackoverflow.com/questions/2390230/do-copyright-dates-need-to-be-updated

A good summary from the second link:

> The copyright notice on a work establishes a claim to copyright. The date on the notice establishes how far back the claim is made. This means if you update the date, you are no longer claiming the copyright for the original date and that means if somebody has copied the work in the meantime and they claim its theirs on the ground that their publishing the copy was before your claim, then it will be difficult to establish who is the originator of the work.
>
> Therefore, if the claim is based on common law copyright (not formally registered), then the date should be the date of first publication. If the claim is a registered copyright, then the date should be the date claimed in the registration. In cases where the work was substantially revised you may establish a new copyright claim to the revised work by adding another copyright notice with a newer date or by adding an additional date to the existing notice as in "© 2000, 2010". Again, the added date establishes how far back the claim is made on the revision.