Use SpecId::is_enabled_in for spec checking

## Summary
```rust
requests_hash: if let SpecId::PRAGUE = evm_spec {
    Some(EMPTY_REQUESTS_HASH)
} else {
    None
},
```

this is not really okay, bc once we upgrade to whatever comes after prague, we'll still need to use EMPTY_REQUESTS_HASH. but this is just making an if check