Remove another unnecessary cast

.codecov.yaml

@@ -10,6 +10,10 @@ component_management:
       name: C  # this is a display name, and can be changed freely
       paths:
         - c/**
+    - component_id: module_cplusplus
+      name: C++
+      paths:
+        - cplusplus/**
     - component_id: module_csharp
       name: C#
       paths:

rust/src/p0008.rs

@@ -63,7 +63,7 @@ pub fn p0008() -> i128 {
         let slice = &string[i..(i + 13)];
         let mut prod: u64 = 1;
         for c in slice.bytes() {
-            prod *= (c as u32 - '0' as u32) as u64;
+            prod *= (c - b'0') as u64;
         }
         if prod > answer {
             answer = prod;