logs: use extended bounds for log charts

backend/src/appenlight/views/logs.py

@@ -79,7 +79,6 b' def logs_fetch_series(request):'
         filter_settings['start_date'] = now - delta
     filter_settings['end_date'] = filter_settings['start_date'] \
                                   + timedelta(days=7)
-    since_when = filter_settings['start_date']
 
     @request.registry.cache_regions.redis_sec_30.cache_on_arguments(
         'logs_graphs')