[Documentation] Install guide needs to set up git server before creating standard objects
The "Creating standard objects" page assumes the git server is already set up, but the current install guide ordering sets up the git server later. Move the git server guide before "Create standard objects."
TBD: Where? I think I'd personally advocate for "right after the API server guide," since at the moment they're limited to the same machine.
6938: Install guide covers git server before standard objects.
The standard objects page covers creating the arvados git repository,
which requires Git hosting to be set up already. It also feels like
this flows a little nicer because currently the Git server must be on
the same host as the API server.