Followup to r86170: fix reference leak in str.format
diff --git a/Objects/stringlib/string_format.h b/Objects/stringlib/string_format.h
index 5205aa9..4053545 100644
--- a/Objects/stringlib/string_format.h
+++ b/Objects/stringlib/string_format.h
@@ -509,7 +509,6 @@
             goto error;
         }
         Py_DECREF(key);
-        Py_INCREF(obj);
     }
     else {
         /* look up in args */