Documentation/git-clone: Transform description list into item list

Documentation/git-clone: Transform description list into item list

so that the list of examples is formatted in the same way as for
git-fetch, and, more importantly, the different identation for the
code blocks in the examples (compared to the immediately preceding code
blocks from url.txt) doesn't look like misformatted, but is clarified by
the items' bullets.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>