build(deps): bump websockets from 14.2 to 15.0 in /tests/ocpp-server

build(deps): bump websockets from 14.2 to 15.0 in /tests/ocpp-server

Bumps [websockets](https://github.com/python-websockets/websockets) from 14.2 to 15.0.
- [Release notes](https://github.com/python-websockets/websockets/releases)
- [Commits](https://github.com/python-websockets/websockets/compare/14.2...15.0)

---
updated-dependencies:
- dependency-name: websockets
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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