t3206: fix incorrect test name

The name of the test used to indicate that it was testing the `--notes`
option but it was really testing the `format.notes` configuration.
Correct the test name to reflect this.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3206-range-diff.sh

@@ -638,7 +638,7 @@ test_expect_success 'format-patch --range-diff with --notes' '
 	test_cmp expect actual
 '
 
-test_expect_success 'format-patch --range-diff with --notes' '
+test_expect_success 'format-patch --range-diff with format.notes config' '
 	git notes add -m "topic note" topic &&
 	git notes add -m "unmodified note" unmodified &&
 	test_when_finished git notes remove topic unmodified &&