Fix recent clippy lints

src/ops.rs

@@ -380,7 +380,7 @@ fn iastore(machine: &mut Machine) -> Result<()> {
         _ => return Err("Cannot use int as heapref"),
     };
     let index: i32 = machine.cur_stack().pop()?.try_into()?;
-    let value = machine.cur_stack().pop()?.clone();
+    let value = machine.cur_stack().pop()?;
 
     RefCell::borrow_mut(&heap)[index as usize] = value;