🐛 Bug Report

Description

All versioned docs have the same "last updated" info: the time and author when that version was frozen.

Have you read the Contributing Guidelines on issues?

Yes

Steps to reproduce

Check https://docusaurus.io/docs/next/markdown-features/admonitions versus https://docusaurus.io/docs/markdown-features/admonitions: the former has a date that's prior to the latter because the latter is when the 2.0.0-beta.6 folder was created, not the actual doc commit date.

I guess we should freeze the last updated metadata as well? Versioned docs can still be updated though...