Update Buck to latest version

Change-Id: Iec337342e647cf1354467ff52351fdbc9fba1077
diff --git a/BUCK b/BUCK
index 0160c15..547d0e8 100644
--- a/BUCK
+++ b/BUCK
@@ -21,7 +21,6 @@
   name = 'cookbook_tests',
   srcs = glob(['src/test/java/**/*IT.java']),
   labels = ['cookbook-plugin'],
-  source_under_test = [':cookbook-plugin__plugin'],
   deps = GERRIT_PLUGIN_API + GERRIT_TESTS + [
     ':cookbook-plugin__plugin',
   ],