fs-test: fix false positive error at Test Case 12

The error message to be matched is wrong. Fix it.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

test/fs/fs-test.sh

@@ -522,7 +522,7 @@ function check_results() {
 		"TC11: 1MB write to $3.w - content verified"
 
 	# Check lookup of 'dot' directory
-	grep -A4 "Test Case 12 " "$1" | grep -q 'Unable to write file'
+	grep -A4 "Test Case 12 " "$1" | grep -q 'Unable to write'
 	pass_fail "TC12: 1MB write to . - write denied"
 
 	# Check directory traversal