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

This reverts commit d898624e53f8e61ba523403791421df6cdeb4781.

Reason for revert: It is probably depending on aosp/1298633, that we are trying to revert

Bug: 154802847
Change-Id: I701c91d5b5b76f4796e1bfc2444638a3ab2913f3
diff --git a/test/knownfailures.json b/test/knownfailures.json
index cba4bea..ced5723 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -1387,8 +1387,7 @@
                   "960-default-smali",
                   "966-default-conflict",
                   "990-field-trace",
-                  "2034-spaces-in-SimpleName",
-                  "2231-oat-require-app-image"],
+                  "2034-spaces-in-SimpleName"],
         "variant": "jvm",
         "bug": "b/154802847",
         "description": ["Failing on RI. Needs further investigating."]