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>

src/main.rs

@@ -136,7 +136,7 @@ impl log::Log for Logger {
         let duration_s = duration.as_secs_f32();
 
         let location = if let (Some(file), Some(line)) = (record.file(), record.line()) {
-            format!("{}:{}", file, line)
+            format!("{file}:{line}")
         } else {
             record.target().to_string()
         };