Avoid using a suffix (#239)

exercises/02_basic_calculator/01_integers/src/lib.rs

@@ -1,6 +1,7 @@
 fn compute(a: u32, b: u32) -> u32 {
     // TODO: change the line below to fix the compiler error and make the tests pass.
-    a + b * 4u8
+    let multiplier: u8 = 4;
+    a + b * multiplier
 }
 
 #[cfg(test)]