Fix clippy::unnecessary_semicolon warning

```
error: unnecessary semicolon
   --> tools/codegen/src/main.rs:251:10
    |
251 |         };
    |          ^ help: remove
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_semicolon
    = note: `-D clippy::unnecessary-semicolon` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_semicolon)]`
```

tools/codegen/src/main.rs

@@ -248,7 +248,7 @@ fn main() -> Result<()> {
         if skip_existing_manifest_versions && existing_manifest.is_some() {
             eprintln!("Skipping {semver_version} already in manifest");
             continue;
-        };
+        }
 
         let mut download_info = BTreeMap::new();
         let mut pubkey = None;