Avoid except in smaps implementation

The caller of this code handles errors gracefully but in this particular spot we
panic if the smaps file cannot be read to string. This is unfortunately a race
condition that we hit in practice.

Signed-off-by: Brian L. Troutwine <[email protected]>

lading/src/observer/memory.rs

@@ -57,8 +57,7 @@ impl Rollup {
         let mut file: std::fs::File = std::fs::OpenOptions::new().read(true).open(path)?;
 
         let mut contents = String::with_capacity(SMAP_SIZE_HINT);
-        file.read_to_string(&mut contents)
-            .expect("Failed to read contents into string");
+        file.read_to_string(&mut contents)?;
 
         Self::from_str(&contents)
     }