Fix formatting for urls section of fetch, pull, and push manpages

Fix formatting for urls section of fetch, pull, and push manpages

The line:

[remote "<remote>"]

was getting swallowed up by asciidoc, causing a critical line in the
explanation for how to store the .git/remotes information in .git/config
to go missing from the git-fetch, git-pull, and git-push manpages.

Put all of the examples into delimited blocks to fix this problem and to
make them look nicer.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Junio C Hamano <junkio@cox.net>