Copyright information in mkdocs.yml need an update for v3.

[bact]

spdx-spec/mkdocs.yml

Line 2 in 3c7fb71

copyright: DRAFT version generated from d25ae89 (model) by 85e8d65 (parser)

This copyright value in mkdocs.yml will be displayed at the bottom of each page in https://spdx.github.io/spdx-spec/v3.0/

Currently it refers to the model at the commit point d25ae89 (from 11 Jan 2024) and the parser at the commit 85e8d65 (12 Jan 2024). So obviously we need an update at least for these hashes or otherwise decide what to put in this "copyright" line.