Bump browserify-sign from 4.2.0 to 4.2.1 (#14636)

Bumps [browserify-sign](https://github.com/crypto-browserify/browserify-sign) from 4.2.0 to 4.2.1.
- [Release notes](https://github.com/crypto-browserify/browserify-sign/releases)
- [Commits](https://github.com/crypto-browserify/browserify-sign/compare/v4.2.0...v4.2.1

)

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