pull: do not abuse 'break' inside a shell 'case'

It is not C. The code would break under mksh when 'pull.ff' is set:

  $ git pull
  /usr/lib/git-core/git-pull[67]: break: can't break
  Already up-to-date.

Signed-off-by: Jacek Konieczny <jajcus@jajcus.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-pull.sh

@@ -58,11 +58,9 @@ pull_ff=$(git config pull.ff)
 case "$pull_ff" in
 false)
 	no_ff=--no-ff
-	break
 	;;
 only)
 	ff_only=--ff-only
-	break
 	;;
 esac