Depsgraph: tag relations update from Set Active Object As Camera.

Dependency building assumes scene.camera is fixed due to #107081.
Thus it is necessary to do a relations update when it does change.

Pull Request #110139

source/blender/editors/space_view3d/view3d_view.cc

@@ -240,6 +240,7 @@ static int view3d_setobjectascamera_exec(bContext *C, wmOperator *op)
     if (v3d->scenelock && scene->camera != ob) {
       scene->camera = ob;
       DEG_id_tag_update(&scene->id, ID_RECALC_COPY_ON_WRITE);
+      DEG_relations_tag_update(CTX_data_main(C));
     }
 
     /* unlikely but looks like a glitch when set to the same */