Docs pages - page last changed time not correct

[ADBond]

Revision info at bottom of pages is not specific to pages or revisions, but just gives the time of the last site build.

Relevant mkdocs build warning:
[git-revision-date-localized-plugin] Unable to find a git directory and/or git is not installed. Option 'fallback_to_build_date' set to 'true': Falling back to build date

Possibly as docs/ is not itself a git repo - this may have broken when we migrated splink_demos into this repo.

[ADBond]

This also contributes quite a bit of noise to the docs build logs (though is not the only culprit)

[ADBond]

While the plugin is now functioning correctly, it is not running correctly in github actions, as currently not enough git history is available in the context in which it runs:

WARNING:root:
                [git-revision-date-localized-plugin] Running on GitHub Actions might lead to wrong
                Git revision dates due to a shallow git fetch depth.

                Try setting fetch-depth to 0 in your GitHub Action
                (see https://github.com/actions/checkout).
                

[ADBond]

No longer using this plugin with Splink 4 docs