Update rppal requirement from 0.19.0 to 0.20.0

Updates the requirements on [rppal](https://github.com/golemparts/rppal) to permit the latest version.
- [Release notes](https://github.com/golemparts/rppal/releases)
- [Changelog](https://github.com/golemparts/rppal/blob/master/CHANGELOG.md)
- [Commits](golemparts/rppal@0.19.0...0.20.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -21,7 +21,7 @@ embedded-hal-bus = { version = "0.2.0", features = ["std"] }
 eyre = "0.6.9"
 log = "0.4.20"
 pretty_env_logger = "0.5.0"
-rppal = { version = "0.19.0", features = ["hal"] }
+rppal = { version = "0.20.0", features = ["hal"] }
 serde_test = "1.0.176"
 
 [features]