Remove api-review workflow after Validation Framework v1 lands in main

[hdamker]

Problem description

The api-review reusable workflow and its supporting code
(.github/workflows/api-review-reusable.yml,
scripts/api_review_validator_v0_6.py, the api-review/ directory
with its own workflows and documentation) were the v0 approach to
API review automation. They have been functionally superseded by the
Validation Framework v1
(camaraproject/ReleaseManagement#448), which implements equivalent
and expanded checks on a different architecture.

The only consumer of the reusable workflow is the caller workflow
deployed in camaraproject/ReleaseManagement. No API repository uses
the api-review workflow directly.

Possible evolution

Once the validation-framework branch lands in main and Validation
Framework v1 has taken over API review at CAMARA scale, remove the
api-review workflow and its supporting code:

• In camaraproject/tooling:
  • .github/workflows/api-review-reusable.yml
  • scripts/api_review_validator_v0_6.py
  • api-review/ directory (trigger workflow, usage guide, any
    other supporting assets)
  • README references to the api-review workflow
• In camaraproject/ReleaseManagement:
  • The caller workflow invoking the reusable workflow (the only
    deployment of the caller across the organization)

Dependencies / relationship to other work

• Implement CAMARA Validation Framework v1 ReleaseManagement#448 (Validation Framework v1)
  — removal should not begin until VF v1 has landed in `main` and
  is the documented API-review path for CAMARA.
• Validation Framework: progressive rollout to API repositories and v1 GA ReleaseManagement#484 (progressive rollout + v1
  GA) — the wider rollout context, though the api-review removal is
  a one-time cleanup and not gated by the progressive stage flip.

Additional context

This issue tracks a one-time removal, not ongoing work. It does not
replace any capability — the Validation Framework fully covers the
checks the api-review workflow used to perform.