Increased default payload limit from 100 kB to 300 kB (#26651)

server/public/model/config.go

@@ -918,7 +918,7 @@ func (s *ServiceSettings) SetDefaults(isUpdate bool) {
 	}
 
 	if s.MaximumPayloadSizeBytes == nil {
-		s.MaximumPayloadSizeBytes = NewInt64(100000)
+		s.MaximumPayloadSizeBytes = NewInt64(300000)
 	}
 }