chore: move the aptos smoke workflow off aptos-init

[cawthorne]

Summary

• move the Aptos smoke workflow off the old aptos-init core branch
• temporarily point the smoke workflow at the paired chainlink PR branch until smartcontractkit/chainlink#21828 merges
• explicitly opt the generated core TOML into mock-streams-trigger@1.0.0 so the existing workflow smoke path still works with gated core registration
• make the PR-body override accept the documented core_ref:<ref>; syntax
• remove the stale README note that said develop could not work yet

Depends on

• smartcontractkit/chainlink#21828

Follow-up after merge

• switch .github/workflows/aptos-run-smoke-tests.yml from feature/aptos-develop-mock-trigger to plain develop

Testing

• bash .github/actions/get-core-ref/test_get_core_ref.sh
• parsed integration-tests/templates/core.toml through the chainlink TOML types from feature/aptos-develop-mock-trigger
• full smoke run is still blocked locally in this session because the Docker daemon is not running