Modify severity of 'Scheduler::reportRetrieveJobsBatch()' log message to INFO

The following log message has an ERROR severity, but should probably be only INFO.

[1660311444.396973000] Aug 12 15:37:24.396973 tpsrv327.cern.ch cta-taped: LVL="ERROR" PID="7722" TID="7722" MSG="In Scheduler::reportRetrieveJobsBatch(): reported a batch of retrieve jobs." SubprocessName="maintenanceHandler" totalReports="2" failedReports="0" successfulReports="2" getRetrieveJobsToReportTime="13.323224" asyncReportLaunchTime="0.000065" reportCompletionTime="0.000010" queueAndSwitchStateTime="0.056470" reportRecordingInSchedDbTime="0.000243"

https://gitlab.cern.ch/cta/CTA/-/blame/main/scheduler/Scheduler.cpp#L2055