Bump elliptic from 6.5.3 to 6.5.4 in /docs-source

Bumps [elliptic](https://github.com/indutny/elliptic) from 6.5.3 to 6.5.4.
- [Release notes](https://github.com/indutny/elliptic/releases)
- [Commits](indutny/elliptic@v6.5.3...v6.5.4)

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