tech-debt: Re-enable end_tx tests that depended on SSTORE

[CPerezz]

In #312 we left some tech debt as some tests for EndTx could not be done due to SSTORE not being implemented.

Now that it is, we should be able to brind them back and pay this tech debt.

See:

zkevm-circuits/zkevm-circuits/src/evm_circuit/execution/end_tx.rs

Lines 332 to 345 in 50d3ad2

	fn end_tx_gadget_simple() {
	// TODO: Enable this with respective code when SSTORE is implemented.
	// Tx with non-capped refund
	// test_ok(vec![mock_tx(
	// address!("0x00000000000000000000000000000000000000fe"),
	// Some(27000),
	// None,
	// )]);
	// Tx with capped refund
	// test_ok(vec![mock_tx(
	// address!("0x00000000000000000000000000000000000000fe"),
	// Some(65000),
	// None,
	// )]);