chore: mark code snippet in README.md no_run

Signed-off-by: Kaspar Schleiser <kaspar@schleiser.de>

Author: kaspar030

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- fix "unit tests in doctest are not executed" clippy warning
+
 ## [0.7.0]
 
 ### Added

README.md

@@ -87,7 +87,7 @@ the [FAQ and common Errors](https://github.com/probe-rs/embedded-test/wiki/FAQ-a
 Check the [example folder](https://github.com/probe-rs/embedded-test/tree/master/examples)
 for a complete example project for stm32/esp32.
 
-```rust
+```rust,no_run
 #![no_std]
 #![no_main]