Fix c/p error in inline documentation (#29148)

Fix small copy/paste error in inline documentation

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

services/auth/source/db/source.go

@@ -18,7 +18,7 @@ func (source *Source) FromDB(bs []byte) error {
 	return nil
 }
 
-// ToDB exports an SMTPConfig to a serialized format.
+// ToDB exports the config to a byte slice to be saved into database (this method is just dummy and does nothing for DB source)
 func (source *Source) ToDB() ([]byte, error) {
 	return nil, nil
 }