Unnecessary Successful Backup Messages
Trace Flag 3226 | Suppress Successful Backup Messages
By default, every successful backup operation adds an entry in the SQL Server error log and the system event log. If you create very frequent log backups, these success messages accumulate quickly, resulting in huge error logs in which finding other messages is problematic. With this trace flag, you can suppress these log entries. This is useful if you run frequent log backups and none of your scripts depends on those entries.
Enable TF3226 on startup using startup parameters.
SCM Services - Configure Server Startup Options | Microsoft Docs
DBCC TRACEON - Trace Flags (Transact-SQL) | Microsoft Docs