chore: remove manual Index section from Promotions & Taxes API overview

[PedroAntunesCosta]

Why

Until last week, the API reference overview page on the Developers Portal rendered as a client-side RapiDoc embed. Because Google sees almost no server-rendered content on those pages, our API reference overviews were not being indexed and the overview content (description, list of endpoints, etc.) was effectively invisible to search engines.

vtexdocs/devportal#1226 (EDU-16758) fixed this by:

• Server-rendering the overview content above RapiDoc (<h1> title + full markdown description + auto-generated Endpoints table).
• Building richer meta descriptions (API description + top operation summaries).
• Adding self-referencing canonical tags, removing noindex, and enabling ISR.

Because the new renderer now generates the Endpoints section automatically from each spec's paths, the manually-maintained ## Index section that we used to write inside every info.description is now redundant. Keeping both would mean the same endpoint list appears twice on every overview page.

What this PR does

Removes the ## Index section from VTEX - Promotions & Taxes API.json's info.description. No other field is touched. The auto-generated Endpoints section on the Developers Portal continues to list every operation in the spec.

Verification

• info.description is still valid markdown and ends cleanly at the previous section's last paragraph (or at the next ## Heading).
• The spec remains valid OpenAPI 3.0 (git diff only touches the description line).
• On a local preview of the Developers Portal, the overview page renders the description without the duplicated index, and the auto-generated Endpoints section lists every operation.

Related

• vtexdocs/devportal#1226 — Improve API reference SEO and indexing (EDU-16758)

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Types of changes

• New content (endpoints, descriptions or fields from scratch)
• Improvement (make an endpoint's title or description even better)
• Spelling and grammar accuracy (self-explanatory)

Changelog

Do not forget to update your changes to our Developer Portal's changelog. Did you create a release note?

• Yes, I already created a release note about this change.
• Not yet, but I'm going to.
• No, it's just a fix.

[github-actions]

Thanks for your contribution. The .json file will be checked now with Spectral.