fix 'derivable_impl' clippy warning

Signed-off-by: Joseph Livesey <jlivesey@gmail.com>

validator/src/journal/block_wrapper.rs

@@ -21,21 +21,16 @@ use std::fmt;
 
 use cpython::{self, ObjectProtocol, PyClone, PyObject};
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
 pub enum BlockStatus {
+    #[default]
     Unknown = 0,
     Invalid = 1,
     Valid = 2,
     Missing = 3,
     InValidation = 5,
 }
 
-impl Default for BlockStatus {
-    fn default() -> Self {
-        BlockStatus::Unknown
-    }
-}
-
 #[derive(Debug)]
 pub struct BlockWrapper {
     pub(super) py_block_wrapper: PyObject,