Blacklist 596-app-image.

bug: 70734839
Change-Id: I1c391381d8bf6b69b13ea92317b7025a062ff60f
diff --git a/test/knownfailures.json b/test/knownfailures.json
index 80b262d..d390c4c 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -276,7 +276,8 @@
     },
     {
         "tests": "596-app-images",
-        "variant": "npictest"
+        "description": "Code being tested has been disabled",
+        "bug": "b/70734839"
     },
     {
         "tests": "055-enum-performance",