De-duplicate start a light node pages

[rootulp]

https://docs.celestia.org/how-to-guides/quick-start#run-a-light-node is duplicative of https://docs.celestia.org/how-to-guides/light-node#start-the-light-node

The latter seems preferable b/c it has copy + paste commands for all three networks but it doesn't have the commands to sync from a more recent height

Proposal

Remove the first one, keep the second one, add the commands to sync from a more recent height