Fix missing comma in knownfailures.json

Test: testrunner.py ...
Change-Id: I3c23b9be732074cacde8db75c9da0da4ead98ac9
diff --git a/test/knownfailures.json b/test/knownfailures.json
index 6f796da..e03bd68 100644
--- a/test/knownfailures.json
+++ b/test/knownfailures.json
@@ -350,7 +350,7 @@
                   "080-oom-throw"],
         "bug": "http://b/36377828",
         "variant": "interp-ac"
-    }
+    },
     {
         "tests": "638-checker-inline-caches",
         "description": ["Disable 638-checker-inline-caches temporarily until a fix",