Remove git-annex

[matchboxbananasynergy]

This seems to be another legacy recommendation that could be removed. The usecase for it seems very niche, and it pales in comparison to our other recommendations.

We list Syncthing along with it, which is very well known and respected, and supports Android very well.

At the very least, I would want to place Syncthing on top of Git-annex, but ideally, I think we can remove it completely to streamline our recommendations to just the best options for each category.

[ghost]

Yeah git rid of it

[dngray]

I think syncthing is more useful, can do over QUIC, and has the whole relay thing/discovery thing.

I don't see much use for git-annex myself.

[matchboxbananasynergy]

Done in privacyguides/privacyguides.org#1486