Bump matrix-js-sdk from 15.5.2 to 15.6.0 (#347)

Bump matrix-js-sdk from 15.5.2 to 15.6.0 (#347)

Bumps [matrix-js-sdk](https://github.com/matrix-org/matrix-js-sdk) from 15.5.2 to 15.6.0.
- [Release notes](https://github.com/matrix-org/matrix-js-sdk/releases)
- [Changelog](https://github.com/matrix-org/matrix-js-sdk/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/matrix-org/matrix-js-sdk/compare/v15.5.2...v15.6.0)

---
updated-dependencies:
- dependency-name: matrix-js-sdk
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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