docs: update storage requirements for full storage nodes / validators

[jcstein]

Problem

Docs requirements are too low for full state sync from snapshot and from genesis.

see https://snaps.qubelabs.io/celestia/

• mainnet is 1.6 TB
• mocha is 1.1 TB

Solution

increase storage requirements to ~2 TB note that state growth will always increase for full state sync (from Callum: "Having hardware requirements stated for a non pruning problem is a bit difficult because it's sort of a moving target (storage will forever get bigger).")