Update rtt-target requirement in /examples/gpiote-demo (#508)

Updates the requirements on [rtt-target](https://github.com/probe-rs/rtt-target) to permit the latest version.
- [Release notes](https://github.com/probe-rs/rtt-target/releases)
- [Commits](probe-rs/rtt-target@v0.5.0...rtt-target-v0.6.0)

---
updated-dependencies:
- dependency-name: rtt-target
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

examples/gpiote-demo/Cargo.toml

@@ -10,5 +10,5 @@ cortex-m-rt = { version = "0.7.0", features = ["device"] }
 cortex-m-rtic = { version = "1.0.0", default-features = false }
 embedded-hal = "1.0.0"
 systick-monotonic = "1.0.0"
-rtt-target = "0.5.0"
+rtt-target = "0.6.0"
 nrf52840-hal = { features = ["rt"], path = "../../nrf52840-hal" }