Update docs for ns-viewer (#1892)

docs/quickstart/first_nerf.md

@@ -38,8 +38,6 @@ It is possible to load a pretrained model by running
 ns-train nerfacto --data data/nerfstudio/poster --load-dir {outputs/.../nerfstudio_models}
 ```
 
-This will automatically start training. If you do not want it to train, add `--viewer.start-train False` to your training command.
-
 ## Visualize existing run
 
 Given a pretrained model checkpoint, you can start the viewer by running