fix staterestore (#375)

libafl/src/observers/cmp.rs

@@ -45,24 +45,13 @@ impl CmpValues {
 }
 
 /// A state metadata holding a list of values logged from comparisons
-#[derive(Default, Deserialize)]
+#[derive(Default, Serialize, Deserialize)]
 pub struct CmpValuesMetadata {
     /// A `list` of values.
     #[serde(skip)]
     pub list: Vec<CmpValues>,
 }
 
-/// Implement an empty serializer as we do not need to keep this metadata in State after a restore
-impl Serialize for CmpValuesMetadata {
-    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    where
-        S: Serializer,
-    {
-        let list: Vec<CmpValues> = vec![];
-        list.serialize(serializer)
-    }
-}
-
 crate::impl_serdeany!(CmpValuesMetadata);
 
 impl AsSlice<CmpValues> for CmpValuesMetadata {