blockdev: Fix formatting

Apply cargo fmt to fix line wrapping in run_loopback_cleanup_helper.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

Author: ericcurtin

crates/blockdev/src/blockdev.rs

@@ -433,7 +433,8 @@ pub async fn run_loopback_cleanup_helper(device_path: &str) -> Result<()> {
         // SIGTERM = 15
         let ret = prctl(PR_SET_PDEATHSIG, libc::SIGTERM as libc::c_ulong);
         if ret != 0 {
-            return Err(std::io::Error::last_os_error()).context("Failed to set parent death signal");
+            return Err(std::io::Error::last_os_error())
+                .context("Failed to set parent death signal");
         }
     }