chore(deps): update stellar/binaries action to v21

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
stellar/binaries	action	major	v20 -> v21

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Release Notes

stellar/binaries (stellar/binaries)

### [`v21`](https://togithub.com/stellar/binaries/releases/tag/v21) [Compare Source](https://togithub.com/stellar/binaries/compare/v20...v21) #### What's Changed - Build binaries for macOS amd64 and arm64 by [@​leighmcculloch](https://togithub.com/leighmcculloch) in [https://github.com/stellar/binaries/pull/20](https://togithub.com/stellar/binaries/pull/20) **Full Changelog**: https://github.com/stellar/binaries/compare/v20...v21

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Configuration

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