Remove ri_child_tax_rebate from state_ctcs catalog

[PavelMakarchuk]

Closes #8149.

Summary

Remove `ri_child_tax_rebate` from `parameters/gov/states/household/state_ctcs.yaml` at all year entries (2021, 2022, 2023, 2024, 2026).

Why

The Rhode Island Child Tax Rebate was a one-time 2022 program under R.I. Gen. Laws § 44-30-103 — checks based on 2021 returns, not an ongoing tax credit. It does not belong in the ongoing state CTC catalog parameter.

Its presence produced phantom values in 2023+ via `taxsim_state_ctc` (which aggregates `gov.states.household.state_ctcs`), surfacing as incorrect `sctc` output in `policyengine-taxsim`. Same pattern as #8146 (CT child tax rebate, fixed via #8147).

Verification

Confirmed with an RI joint 2025 filer with two children:

Variable	Before	After
`taxsim_state_ctc`	$500 (phantom)	$0 ✓
`ri_child_tax_rebate` (standalone)	$500	$500

The standalone `ri_child_tax_rebate` variable still computes its result; only the catalog entry is removed, matching the issue's ask.

Related cleanup (not in this PR, per issue)

• Add `2023-01-01: 0` to `parameters/gov/states/ri/tax/income/credits/child_tax_rebate/amount.yaml` so the variable returns $0 post-2022.
• Consider whether the start date should be 2022-01-01 rather than 2021-01-01 (the parameter's own reference comment notes "The child tax rebate was introduced in 2022").

Flagged as non-blocking in the issue; can be a follow-up.

Test plan

• `make format` clean
• End-to-end verification: `taxsim_state_ctc` for RI 2025 = $0 (previously $500 phantom)

🤖 Generated with Claude Code