doc: difference in location to apply is "offset", not "fuzz"

The documentation to "git rebase" says that the line numbers (in the rebased change) may not exactly be the same as the line numbers the change gets replayed on top of the new base, but uses a wrong noun "fuzz". It should have said "offset". They are both terms of art. "fuzz" is about context lines not exactly matching. "offset" is about the difference in the location that a change was taken from the original and the change gets replayed on the target. "offset" is often inevitable and part of normal life. "fuzz" on the other hand is often a sign of trouble (and indeed "Git" refuses to apply a change with "fuzz", except there are options to be fuzzy about whitespaces). Signed-off-by: Junio C Hamano <gitster@pobox.com>