fix(tvix/eval): address all current clippy lints

Change-Id: I758fc4f3b9078de7ca6228a75a4351c3e085c4cf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6272
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

tvix/eval/src/value/builtin.rs

@@ -58,7 +58,7 @@ impl Builtin {
         }
 
         // Function is not yet ready to be called.
-        return Ok(Value::Builtin(self));
+        Ok(Value::Builtin(self))
     }
 }