disaster recovery `account backup` and `restore` docs are outdated

[davemo88]

Hello,

These parts of the docs are outdated, e.g. referring to non-existent options like --data and --no-progress for nats account backup. It also says

The nats account restore tool does not support restoring data

which is incorrect.

I was going to make a PR to update the docs but I don't really know best practices or how this works in depth, so I'm just opening an issue in hopes somebody more knowledgeable can correct these docs.