lab5: Simplify input reading template for Rust

hugo/content/docs/cviceni/lab5/_index.md

@@ -121,14 +121,11 @@ potřeba uvolnit funkcí `free()`.
 {{< tab "Rust" >}}
 ```rust
 for line in std::io::stdin().lock().lines().map(|l| l.unwrap()) {
-    match line.split_once(' ') {
-        Some((num, word)) => {
-            let x = num.parse::<usize>()?;
-            // ....
-        }
-        None => {
-            // ...
-        }
+    if let Some((num, word)) = line.split_once(' ') {
+        let x = num.parse::<usize>()?;
+        // ...
+    } else {
+        // ...
     };
 }
 ```