Drop unused Manager member retry_interval

Author: cgzones

src/netlog/netlog-manager.h

@@ -36,7 +36,6 @@ struct Manager {
         sd_event *event;
 
         sd_event_source *event_journal_input;
-        usec_t retry_interval;
         usec_t connection_retry_usec;
 
         sd_event_source *sigint_event, *sigterm_event;