Bump elliptic from 6.5.3 to 6.5.4 in /demo (#163)

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)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>