runtime-rs : fix shim source is ambiguous

In the documentation test, the name shim has multiple potential
sources of import, now give it a clear source.

Fixes: #5535

Signed-off-by: Chen TaoTao <chentt10@chinatelecom.cn>

src/runtime-rs/crates/shim/src/lib.rs

@@ -16,7 +16,7 @@ pub use error::Error;
 mod logger;
 mod panic_hook;
 mod shim;
-pub use shim::ShimExecutor;
+pub use crate::shim::ShimExecutor;
 mod core_sched;
 #[rustfmt::skip]
 pub mod config;