t4014: drop redirections to /dev/null

Since output is silenced when running without `-v` and debugging output
is useful with `-v`, remove redirections to /dev/null as it is not
useful.

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

t/t4014-format-patch.sh

@@ -1502,42 +1502,42 @@ test_expect_success 'cover letter using branch description (1)' '
 	git checkout rebuild-1 &&
 	test_config branch.rebuild-1.description hello &&
 	git format-patch --stdout --cover-letter master >actual &&
-	grep hello actual >/dev/null
+	grep hello actual
 '
 
 test_expect_success 'cover letter using branch description (2)' '
 	git checkout rebuild-1 &&
 	test_config branch.rebuild-1.description hello &&
 	git format-patch --stdout --cover-letter rebuild-1~2..rebuild-1 >actual &&
-	grep hello actual >/dev/null
+	grep hello actual
 '
 
 test_expect_success 'cover letter using branch description (3)' '
 	git checkout rebuild-1 &&
 	test_config branch.rebuild-1.description hello &&
 	git format-patch --stdout --cover-letter ^master rebuild-1 >actual &&
-	grep hello actual >/dev/null
+	grep hello actual
 '
 
 test_expect_success 'cover letter using branch description (4)' '
 	git checkout rebuild-1 &&
 	test_config branch.rebuild-1.description hello &&
 	git format-patch --stdout --cover-letter master.. >actual &&
-	grep hello actual >/dev/null
+	grep hello actual
 '
 
 test_expect_success 'cover letter using branch description (5)' '
 	git checkout rebuild-1 &&
 	test_config branch.rebuild-1.description hello &&
 	git format-patch --stdout --cover-letter -2 HEAD >actual &&
-	grep hello actual >/dev/null
+	grep hello actual
 '
 
 test_expect_success 'cover letter using branch description (6)' '
 	git checkout rebuild-1 &&
 	test_config branch.rebuild-1.description hello &&
 	git format-patch --stdout --cover-letter -2 >actual &&
-	grep hello actual >/dev/null
+	grep hello actual
 '
 
 test_expect_success 'cover letter with nothing' '