example fix

Author: SKHDev195

zkllvm/best-practices-limitations/rust-derive.mdx

@@ -44,20 +44,18 @@ When `assigner` is called on a circuit with this struct, the circuit IR would co
 To avoid this problem, use the `#[repr(C)]` directive:
 
 ```rust
+
+use ark_pallas::Fq;
+
+type BlockType = [Fq; 2];
+
 #[repr(C)]
 #[derive(Copy, Clone)]
 pub struct BlockDataType {
     prev_block_hash: BlockType,
     data: BlockType,
-    validators_signatures: [EdDSASignatureType; 4],
-    validators_keys: [EdwardsAffine; 4],
-}
-
-#[repr(C)]
-#[derive(Copy, Clone)]
-pub struct EdDSASignatureType {
-    r: EdwardsAffine,
-    s: Fr,
+    validators_signature: i32,
+    validators_key: u64,
 }
 ```