cmd: simplify project nesting info in init

[jorgeorpinel]

Notes extracted from #1661:

Ideally not but yes in the way things are structured now in this ref. This isolation and nested situation got too complicated... I should probably make a separate sub-section to cover it after explaining all the 3 kinds of projects (typical or git-enabled, --subdir, --no-scm).

On Git submodules: "I would expect from people who use submodules have the same intuition by default - isolated in Git, isolated in DVC - nothing special or specif", "True, I can just remove it and handle them via support channel if needed" (from #1615 (review))

On block code examples for nested repos: ".git still not important here" (from #1615 (review))

[shcheklein]

@jorgeorpinel I think it was in a decent shape. Let's leave as is for now?

[jorgeorpinel]

Yeah sorry, I couldn't help myself from pushing these changes. Only took me like 10 min. Basically the code block examples in --subdir are removed, this simplifies the cmd ref a little. Everything else are copy edits. See https://dvc-landing-cmd-init-ne-juucow.herokuapp.com/doc/command-reference/init

But if you prefer to close this that's also OK, I'll re-apply the copy edits in a small regular updates PR that I probably need to submit tomorrow. Thanks

[shcheklein]

@jorgeorpinel we have some unrelated changes here now? was it intentional?

I still don't see a strong reason to touch it (except small copy edits). Let's create a ticket if needed, prioritize and discuss it there first.

[jorgeorpinel]

some unrelated changes here now?

Oops those were meant for another branch...