Fixup a few 2023 copyright years

Attached is a patch which adjusts the copyright years of 2023 that
have crept in this year from patches that were written last year and
committed without adjusting this to 2024.

The patch isn't produced by src/tools/copyright.pl as that'll
transform files which are new and only contain "2023" to become
"2023-2024", which I don't believe is what we want in this case.

No other matches aside from .po files from:
git grep -e "Copyright" --and --not -e "2024" --and -e "PostgreSQL
Global Development Group"

Should we do this and is this a good time to?

David