chore: no need to reset datalayer._needsFetch after a save

It is reset only after loading the layer data.

Co-authored-by: David Larlet <david@larlet.fr>

umap/static/umap/js/modules/data/layer.js

@@ -1161,7 +1161,6 @@ export class DataLayer extends ServerStored {
       this.backupOptions()
       this.backupData()
       this.connectToMap()
-      this._needsFetch = false
       this.redraw() // Needed for reordering features
       return true
     }