Remove Git 2.37 workaround from install docs

[adamchainz]

The bug was fixed in Git 2.38, as noted on original issue: #1114 (comment)

I guess we can remove this from the docs now, so new users don’t switch to the old interactive add.

I thought of adding a section “If you’re using Git 2.37...” but that seemed too specific. If anyone encounters the error, hopefully they’ll search for it and see they need to upgrade Git.

[adamchainz]

It also seems the workaround was never added to the docs: https://github.com/dandavison/delta/blob/master/manual/src/get-started.md

Perhaps removing the GitHub README and pointing only to the docs site would be a good idea, to reduce redundant redundancy (that is redundant).

[dandavison]

Thanks @adamchainz! I agree. I think I do like having the quick start instructions in the Github README landing page so that people who are used to installing and configuring things like this can do it very quickly without any clicking around.

[adamchainz]

Thanks for the fast review. Fair enough on keeping on GitHub.