tests: remove most uses of test_i18ncmp

As a follow-up to d162b25f956 (tests: remove support for
GIT_TEST_GETTEXT_POISON, 2021-01-20) remove most uses of test_i18ncmp
via a simple s/test_i18ncmp/test_cmp/g search-replacement.

I'm leaving t6300-for-each-ref.sh out due to a conflict with in-flight
changes between "master" and "seen", as well as the prerequisite
itself due to other changes between "master" and "next/seen" which add
new test_i18ncmp uses.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh
index 5e88a10..587b408 100755
--- a/t/t3400-rebase.sh
+++ b/t/t3400-rebase.sh
@@ -113,7 +113,7 @@
 	test_cmp expect.forkpoint actual.forkpoint &&
 	# the next one is dubious---we may want to say "-",
 	# instead of @{-1}, in the message
-	test_i18ncmp expect.messages actual.messages
+	test_cmp expect.messages actual.messages
 '
 
 test_expect_success 'rebase a single mode change' '