docs: add tables of networks supported by data api

[michaelmanzano-alc]

Summary

This PR adds explicit supported networks documentation to the Token API, Transfers API, NFT API, Prices API, and Portfolio API documentation pages. Previously, users had to navigate to the dashboard to find which networks each API supported.

Changes

Added Supported Networks Sections

Added a "Supported Networks" section to each API's overview/quickstart page:

• fern/api-reference/data/token-api/token-api-overview.mdx
• fern/api-reference/data/transfers-api/transfers-api-quickstart.mdx
• fern/api-reference/data/prices-api/prices-api-quickstart.mdx
• fern/api-reference/data/nft-api/nft-api-overview.mdx
• fern/api-reference/data/portfolio-apis/portfolio-apis.mdx

Each section includes:

• A one-line usage hint explaining how to use network slugs for that API
• Separate tables for Mainnets and Testnets
• An <Info> callout linking to the Chains dashboard

Cleanup

• Removed redundant Promise .then() code examples from Token API Quickstart
• Removed redundant "Via Node Fetch" section from Prices API Quickstart

Testing

• Verified no linting errors in modified files
• Tables render correctly in markdown preview

[github-actions]

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