Remove explicit copyright end year from LICENSE

[ddabble]

Proposed changes

Constantly having to keep this year updated to the present year seems to simply be a long-standing norm in the open source community, rather than something that's legally required.

There doesn't seem to be a consensus on exactly what to remove and what to keep, however, so replacing the end year with "present" seems like the most conservative option that still removes the need to constantly keep the year updated.

This was inspired by https://github.com/tox-dev/tox/pull/2941, which also links to a couple other "testimonies":

• https://daniel.haxx.se/blog/2023/01/08/copyright-without-years/
• https://hynek.me/til/copyright-years/

Areas to review closely

Checklist

(If any of the points are not relevant, mark them as checked)

• [x] Created tests that fail without the changes, if relevant/possible
• [x] Made sure that your code conforms to the code style guides and that any common code smells have been addressed
  • (It's not intended that you read through this whole document, but that you get yourself an overview over its contents, and that you keep it in mind while taking a second look at your code before opening a pull request)
• [x] Added sufficient documentation - e.g. as docstrings or in the README, if suitable
• [x] Added your changes to the "Unreleased" section of the changelog - mainly the changes that are of particular interest to users and/or developers, if any
• [x] Added a "Deployment notes" section above, if anything out of the ordinary should be done when deploying these changes to the server

[codecov[bot]]

Codecov Report

Merging #624 (4e712cf) into dev (fec470f) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev     #624   +/-   ##
=======================================
  Coverage   87.27%   87.27%           
=======================================
  Files         135      135           
  Lines        5672     5672           
=======================================
  Hits         4950     4950           
  Misses        722      722