Dead links and undocumented API behavior in developer docs

[BrandonFilth]

Found several issues in the docs while building on Astar EVM:

1. OnFinality NFT API page references a dead service

Page: https://docs.astar.network/docs/build/integrations/indexers/onfinality/

The OnFinality Unified NFT API has been shut down:

• nft-beta.api.onfinality.io → "API Deprecated" page
• nft-beta.onfinality.io/public → DNS doesn't resolve

This page should be removed or clearly marked as deprecated.

2. API endpoint docs missing critical info

Page: https://docs.astar.network/docs/build/dapp-staking/indexer/

Missing:

• Response size limits (we confirmed /stakerslist/ truncates silently see /stakerslist/{contractAddress} returns incomplete data missing most stakers dapps-staking-indexer-v3#34)
• Pagination parameters
• Rate limit numbers
• Response schemas

The page says "restricted usage" without defining limits. Developers need concrete
numbers to build reliable integrations.

[Juminstock]

Thank you so much for your reviews to our docs, @BrandonFilth! I'll work on update the parts you mention here.