docs: update validator Omnibus example

[tharune]

Summary

• update validator/private-sentry Omnibus SDL snippets to the current cosmos-omnibus image tag
• update peer and consensus environment variable names to match the upstream private-sentries example
• update the later node-ID replacement examples to use the same current variable names
• normalize the edited YAML snippet indentation so the examples parse cleanly

Verification

• checked the latest akash-network/cosmos-omnibus release: v1.2.43, published 2026-04-20
• checked the official validator-and-private-sentries example, which uses ghcr.io/akash-network/cosmos-omnibus:v1.2.43-akash-v2.0.1
• checked the upstream example variable names: AKASH_P2P_UNCONDITIONAL_PEER_IDS, AKASH_P2P_PRIVATE_PEER_IDS, AKASH_P2P_ADDR_BOOK_STRICT, and AKASH_CONSENSUS_DOUBLE_SIGN_CHECK_HEIGHT
• parsed the edited validator, node1, and node2 YAML snippets with Ruby YAML
• ran rg to confirm the stale image tag and old env names no longer remain in this page
• ran git diff --check