t7500: remove non-existant C_LOCALE_OUTPUT prereq

The C_LOCALE_OUTPUT prerequisite was removed in b1e0798 (tests:
remove last uses of C_LOCALE_OUTPUT, 2021-02-11), where Ævar noted:

    I'm not leaving the prerequisite itself in place for in-flight changes
    as there currently are none that introduce new tests that rely on it,
    and because C_LOCALE_OUTPUT is currently a noop on the master branch
    we likely won't have any new submissions that use it.

One more use of C_LOCALE_OUTPUT did creep in with 3d1bda6 (t7500: add
tests for --fixup=[amend|reword] options, 2021-03-15).  This causes a
number of the tests to be skipped by default:

    ok 35 # SKIP --fixup=reword: incompatible with --all (missing C_LOCALE_OUTPUT)
    ok 36 # SKIP --fixup=reword: incompatible with --include (missing C_LOCALE_OUTPUT)
    ok 37 # SKIP --fixup=reword: incompatible with --only (missing C_LOCALE_OUTPUT)
    ok 38 # SKIP --fixup=reword: incompatible with --interactive (missing C_LOCALE_OUTPUT)
    ok 39 # SKIP --fixup=reword: incompatible with --patch (missing C_LOCALE_OUTPUT)

Remove the C_LOCALE_OUTPUT prerequisite from these tests so they are
not skipped.

Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7500-commit-template-squash-signoff.sh

@@ -413,7 +413,7 @@ test_expect_success 'amend! commit allows empty commit msg body with --allow-emp
 '
 
 test_fixup_reword_opt () {
-	test_expect_success C_LOCALE_OUTPUT "--fixup=reword: incompatible with $1" "
+	test_expect_success "--fixup=reword: incompatible with $1" "
 		echo 'fatal: reword option of --fixup is mutually exclusive with'\
 			'--patch/--interactive/--all/--include/--only' >expect &&
 		test_must_fail git commit --fixup=reword:HEAD~ $1 2>actual &&