missing opcode encoding for DEREF

Co-authored-by: Koh Wei Jie <[email protected]>

Author: TomWambsgans

crates/lean_prover/witness_generation/src/instruction_encoder.rs

@@ -30,6 +30,7 @@ pub fn field_representation(instr: &Instruction) -> [F; N_INSTRUCTION_COLUMNS] {
             shift_1,
             res,
         } => {
+            fields[8] = F::ONE; // DEREF = 1
             fields[3] = F::ZERO; // flag_A = 0
             fields[0] = F::from_usize(*shift_0);
             fields[5] = F::ONE; // flag_C = 1