Update dApp SDK release notes

Updates the published dApp SDK release-note page from the latest @canton-network/dapp-sdk GitHub releases in canton-network/wallet.

Version changes:

• dApp SDK release notes: latest 1.5.1 -> 1.6.0 from @canton-network/dapp-sdk@1.6.0

Validation run by the workflow:

• npm run update:release-notes -- --target dapp-sdk
• git diff --check