Disable ART run-test 2231-oat-require-app-image on the RI.

This new test was added after commit
cc82f79174c0afb3c1974d7926678b2cfef0835f
(https://android-review.googlesource.com/c/platform/art/+/1294079) was
merged. Disable it for now, in order to unblock testing with the RI.

Test: art/test/testrunner/testrunner.py --jvm
Bug: 154802847
Change-Id: Ida594f4be92041b6abd869be65627ecb9443382d
diff --git a/test/knownfailures.json b/test/knownfailures.json
index 68a8101..66d97f9 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -1387,7 +1387,8 @@
                   "960-default-smali",
                   "966-default-conflict",
                   "990-field-trace",
-                  "2029-spaces-in-SimpleName"],
+                  "2029-spaces-in-SimpleName",
+                  "2231-oat-require-app-image"],
         "variant": "jvm",
         "bug": "b/154802847",
         "description": ["Failing on RI. Needs further investigating."]