Tests: Don't hide unexpected error messages in test_files.sh.

Hiding them makes no sense since normally there's no error
when testing the "good" files. With "bad" files errors are
expected and then it makes sense to keep the messages hidden.

tests/test_files.sh

diff --git a/tests/test_files.sh b/tests/test_files.sh
index 2fa8382..0f8a64d 100755
--- a/tests/test_files.sh
+++ b/tests/test_files.sh
@@ -21,7 +21,7 @@
 
 for I in "$srcdir"/files/good-*.xz
 do
-	if test -z "$XZ" || "$XZ" -dc "$I" > /dev/null 2>&1; then
+	if test -z "$XZ" || "$XZ" -dc "$I" > /dev/null; then
 		:
 	else
 		echo "Good file failed: $I"
@@ -29,7 +29,7 @@
 		exit 1
 	fi
 
-	if test -z "$XZDEC" || "$XZDEC" "$I" > /dev/null 2>&1; then
+	if test -z "$XZDEC" || "$XZDEC" "$I" > /dev/null; then
 		:
 	else
 		echo "Good file failed: $I"