agent: Fix clippy empty_line_after_doc_comments

Manually fix `empty_line_after_doc_comments` clippy warning reported by
rust 1.85.1.

```console
error: empty line after doc comment
  --> src/linux_abi.rs:8:1
   |
8  | / /// Linux ABI related constants.
9  | |
   | |_^
10 |   #[cfg(target_arch = "aarch64")]
11 |   use std::fs;
   |       ------- the comment documents this import
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#empty_line_after_doc_comments
   = note: `-D clippy::empty-line-after-doc-comments` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::empty_line_after_doc_comments)]`
   = help: if the empty line is unintentional remove it
```

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

src/agent/src/linux_abi.rs

@@ -5,7 +5,7 @@
 
 use cfg_if::cfg_if;
 
-/// Linux ABI related constants.
+// Linux ABI related constants.
 
 #[cfg(target_arch = "aarch64")]
 use std::fs;