pull doc: correct outdated description of an example

Since f269048754 (fetch: opportunistically update tracking refs,
2013-05-11), the underlying `git fetch` in `git pull <remote> <branch>`
updates the configured remote-tracking branch for <branch>.

However, an example in the 'Examples' section of the `git pull`
documentation still states that this is not the case.

Correct the description of this example.

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-pull.txt

@@ -229,9 +229,9 @@ branch.<name>.merge options; see linkgit:git-config[1] for details.
 $ git pull origin next
 ------------------------------------------------
 +
-This leaves a copy of `next` temporarily in FETCH_HEAD, but
-does not update any remote-tracking branches. Using remote-tracking
-branches, the same can be done by invoking fetch and merge:
+This leaves a copy of `next` temporarily in FETCH_HEAD, and
+updates the remote-tracking branch `origin/next`.
+The same can be done by invoking fetch and merge:
 +
 ------------------------------------------------
 $ git fetch origin