Update defmt requirement from 0.2 to 0.3

Updates the requirements on [defmt](https://github.com/knurling-rs/defmt) to permit the latest version.
- [Release notes](https://github.com/knurling-rs/defmt/releases)
- [Changelog](https://github.com/knurling-rs/defmt/blob/main/CHANGELOG.md)
- [Commits](knurling-rs/defmt@defmt-v0.2.0...defmt-v0.3.0)

---
updated-dependencies:
- dependency-name: defmt
  dependency-type: direct:production
...

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

Cargo.toml

@@ -34,7 +34,7 @@ modular-bitfield = "0.11.0"
 nb = {version = "1", optional = true}
 void = {version = "1", optional = true}
 
-defmt = { version = "0.2", optional = true}
+defmt = { version = "0.3", optional = true}
 log = { version = "0.4", default-features = false, optional = true }
 
 [dev-dependencies]