Drop trailing comma in tools packages

This is not valid in JSON.

Change-Id: I6d02b0e19590d9110ab8b69a53bdd8eb4abb6bc9
diff --git a/services/cr-buildbucket.cfg b/services/cr-buildbucket.cfg
index a69df32..482a484 100644
--- a/services/cr-buildbucket.cfg
+++ b/services/cr-buildbucket.cfg
@@ -303,7 +303,7 @@
     properties: "project:tools"
     properties_j: <<END
       packages: [
-        "fuchsia.googlesource.com/tools/cmd/symbolize",
+        "fuchsia.googlesource.com/tools/cmd/symbolize"
       ]
     END
   }