chore(deps): update rust crate zbus to v5.15.0

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
zbus	dependencies	minor	5.14.0 → 5.15.0

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Release Notes

z-galaxy/zbus (zbus)

v5.15.0

Compare Source

Added

• ✨ Introduce DispatchResult2 with fdo::Result for dispatch futures.
• ✨ Add Builder::build_message_stream.

Changed

• ♻️ Port Interface and dispatch sites to DispatchResult2.

Deprecated

• 🗑️ Deprecate DispatchResult in favour of DispatchResult2.

Documentation

• 📝 Configure docs.rs to build for all supported targets.

Testing

• ✅ Cover D-Bus error name preservation on property setters.
• ✅ Explicitly choose host endianess in a test.

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