Fix typo in remote branch example in git user manual

In Documentation/user-manual.txt the example
 $ git checkout --track -b origin/maint maint
under "Getting updates with git pull", should read
 $ git checkout --track -b maint origin/maint

This was noticed by Ron, and reported through
 http://bugs.debian.org/427502

Signed-off-by: Gerrit Pape <pape@smarden.org>
Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>

Documentation/user-manual.txt

@@ -1682,7 +1682,7 @@ automatically set the default remote branch to pull from at the time
 that a branch is created:
 
 -------------------------------------------------
-$ git checkout --track -b origin/maint maint
+$ git checkout --track -b maint origin/maint
 -------------------------------------------------
 
 In addition to saving you keystrokes, "git pull" also helps you by