debugfs_duplicate_context_creation.sh does an invalid file write to
ensure it fails.  Check of the failure is sufficient, so the error
message from the failure only makes the output unnecessarily noisy.
Hide it.

Fixes: ade38b8ca5ce ("selftest/damon: add a test for duplicate context dirs creation")
Signed-off-by: SeongJae Park <sj@kernel.org>
---
 .../selftests/damon/debugfs_duplicate_context_creation.sh       | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/damon/debugfs_duplicate_context_creation.sh b/tools/testing/selftests/damon/debugfs_duplicate_context_creation.sh
index 4a76e37ef16b..bd6c22d96ead 100755
--- a/tools/testing/selftests/damon/debugfs_duplicate_context_creation.sh
+++ b/tools/testing/selftests/damon/debugfs_duplicate_context_creation.sh
@@ -12,7 +12,7 @@ then
 	exit 1
 fi
 
-if echo foo > "$DBGFS/mk_contexts"
+if echo foo > "$DBGFS/mk_contexts" 2> /dev/null
 then
 	echo "duplicate context creation success"
 	exit 1
-- 
2.39.5