I forgot to generate the relnotes when I did the release, and when
I generated it a couple days later the script picked `today()` instead
of the date on the tag (because it's supposed to be run _before_ tagging
the release), and I didn't notice right away.
Fixes: cad37be6c9 ("docs: add release notes for 23.3.0")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26475>