Update esp-println requirement from 0.7 to 0.8 in /tests/xtensa

Updates the requirements on [esp-println](https://github.com/esp-rs/esp-println) to permit the latest version.
- [Release notes](https://github.com/esp-rs/esp-println/releases)
- [Commits](https://github.com/esp-rs/esp-println/commits)

---
updated-dependencies:
- dependency-name: esp-println
  dependency-type: direct:production
...

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

tests/xtensa/Cargo.toml

@@ -11,7 +11,7 @@ test-helper = { path = "../helper" }
 paste = "1"
 
 [target.xtensa-esp32-none-elf.dependencies]
-esp-println = { version = "0.7", default-features = false, features = ["uart", "esp32"] }
+esp-println = { version = "0.8", default-features = false, features = ["uart", "esp32"] }
 esp32-hal = "0.17"
 xtensa-lx-rt = { version = "0.16", features = ["esp32"] }