t5541: add 'test_i18ngrep's missing filename parameter

The test 'push --no-progress silences progress but not status' runs
'test_i18ngrep' without specifying a filename parameter.  This has
remained unnoticed since its introduction in e304aeba2 (t5541: test
more combinations of --progress, 2012-05-01), because that
'test_i18ngrep' is supposed to check that the given pattern is not
present in its input, and of course it won't find that pattern if its
input is empty (as it comes from /dev/null).  This also means that
this test could miss a potential breakage of 'git push --no-progress'.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5541-http-push-smart.sh

@@ -234,7 +234,7 @@ test_expect_success TTY 'push --no-progress silences progress but not status' '
 	test_commit no-progress &&
 	test_terminal git push --no-progress >output 2>&1 &&
 	test_i18ngrep "^To http" output &&
-	test_i18ngrep ! "^Writing objects"
+	test_i18ngrep ! "^Writing objects" output
 '
 
 test_expect_success 'push --progress shows progress to non-tty' '