feat(wasm-utxo): remove unused variable in P2SH-P2PK test

Remove unused expected_pubkey variable in the singlesig wallet script tests
since it's not being used in the test assertions.

Issue: BTC-2652

Co-authored-by: llm-git <[email protected]>

Author: OttoAllmendinger

packages/wasm-utxo/src/fixed_script_wallet/wallet_scripts/singlesig.rs

@@ -56,7 +56,7 @@ mod tests {
 
         // Get the expected values from the fixture
         let expected_redeem_script = &p2shp2pk_input.redeem_script;
-        let expected_pubkey = p2shp2pk_input
+        p2shp2pk_input
             .partial_sig
             .first()
             .map(|sig| &sig.pubkey)