Clean up year range in copyright statements

[valassi]

Hi @roiser I move your concerns here from #809 (comment) because that PR is now merged and closed

Repeating your and my comments:

<< SR: Really minor comment and I propose not to revert this, but there is no need to bump up the copyright year numbers, see e.g. blog post https://matija.suklje.name/how-and-why-to-properly-write-copyright-statements-in-your-code (got the link from the CERN open source policy office OSPO)

AV: interesting point... i was actually going to propose that we update all copyright statements to be 2020-2024 in the code, now I am a bit less sure after reading your blog post

i must say i still have a preference for having all copyright statements updated to 2020-2024: i mean that post suggests you do not need to update the years, but it is not saying that you should absolutely not do that... I find it visually more clear on the one hand, and on the other hand it IS true that we are continually updating the code... and in any case yes 50-70 years are a long time, so it makes a little difference...

I think I would especialy like a self consistent practice throughout the code: for instance, we put 2020-2024 everywhere, or we put 2020 (or year of first publication if >2020) everywhere... thoughts? >>

[valassi]

I finally updated the copyright range in PR #842, now merged. Closing