[DBBackup] Remove unnecessary flag

-c
--clean

    Output commands to clean (drop) database objects prior to outputting 
the commands for creating them. (Unless --if-exists is also specified, 
restore might generate some harmless error messages, if any objects were 
not present in the destination database.)

    This option is only meaningful for the plain-text format. For the 
archive formats, you can specify the option when you call pg_restore.

https://www.postgresql.org/docs/current/app-pgdump.html