filter-branch: stop suggesting to use grafts

The graft file is deprecated now, so let's use replace refs in the example
in filter-branch's man page instead.

Suggested-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-filter-branch.txt

@@ -288,7 +288,7 @@ git filter-branch --parent-filter \
 or even simpler:
 
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-echo "$commit-id $graft-id" >> .git/info/grafts
+git replace --graft $commit-id $graft-id
 git filter-branch $graft-id..HEAD
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