Change incorrect uses of "remote branch" meaning "remote-tracking"

Change incorrect uses of "remote branch" meaning "remote-tracking"

"remote branch" is a branch hosted in a remote repository, while
"remote-tracking branch" is a copy of such branch, hosted locally.
The distinction is subtle when the copy is up-to-date, but rather
fundamental to understand what "git fetch" and "git push" do.

This patch should fix all incorrect usages in Documentation/ directory.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>