misc: Use variables directly in format! string

Fix clippy warning `uninlined_format_args` reported by rustc rustc
1.89.0 (29483883e 2025-08-04).

```console
warning: variables can be used directly in the `format!` string
   --> block/src/lib.rs:649:17
    |
649 |                 info!("{} failed to create io_uring instance: {}", error_msg, e);
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
    = note: `#[warn(clippy::uninlined_format_args)]` on by default
help: change this to
    |
649 -                 info!("{} failed to create io_uring instance: {}", error_msg, e);
649 +                 info!("{error_msg} failed to create io_uring instance: {e}");
    |
```

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

vmm/src/migration.rs

@@ -21,7 +21,7 @@ pub fn url_to_path(url: &str) -> std::result::Result<PathBuf, MigratableError> {
     let path: PathBuf = url
         .strip_prefix("file://")
         .ok_or_else(|| {
-            MigratableError::MigrateSend(anyhow!("Could not extract path from URL: {}", url))
+            MigratableError::MigrateSend(anyhow!("Could not extract path from URL: {url}"))
         })
         .map(|s| s.into())?;