chore(deps): bump @stellar/stellar-sdk in /frontend

Bumps [@stellar/stellar-sdk](https://github.com/stellar/js-stellar-sdk) from 14.5.0 to 15.1.0.
- [Release notes](https://github.com/stellar/js-stellar-sdk/releases)
- [Changelog](https://github.com/stellar/js-stellar-sdk/blob/master/CHANGELOG.md)
- [Commits](stellar/js-stellar-sdk@v14.5.0...v15.1.0)

---
updated-dependencies:
- dependency-name: "@stellar/stellar-sdk"
  dependency-version: 15.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]