Bump elliptic from 6.5.1 to 6.5.3 in /example

Bumps [elliptic](https://github.com/indutny/elliptic) from 6.5.1 to 6.5.3.
- [Release notes](https://github.com/indutny/elliptic/releases)
- [Commits](indutny/elliptic@v6.5.1...v6.5.3)

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