p4000: use -3000 when promising -3000

The 'log -3000 (baseline)' test accidentally still used -1000 from an
earlier version.

Noticed-by: Lawrence Holding <Lawrence.Holding@cubic.com>
Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/perf/p4000-diff-algorithms.sh

@@ -7,7 +7,7 @@ test_description="Tests diff generation performance"
 test_perf_default_repo
 
 test_perf 'log -3000 (baseline)' '
-	git log -1000 >/dev/null
+	git log -3000 >/dev/null
 '
 
 test_perf 'log --raw -3000 (tree-only)' '