Missing description of system contract `0x2`

[die-herdplatte]

Special addresses 0x0 and 0x1 are described at https://docs.starknet.io/learn/protocol/state#special-addresses, but 0x2 is missing.

See https://community.starknet.io/t/starknet-v0-13-4-pre-release-notes/115257#p-2358763-stateful-compression-11

[tusharrrr1]

Because 0x2's role is strictly tied to state diff compression, it doesn't function like 0x0 or 0x1 and thus isn’t listed among general "special addresses"—the documentation may simply not have been updated to reflect this new use case.