Incorrect return type for web3-v1 events

`web3.eth.Contract().events.SomeEvent(callback)` returns `Subscription` object but the generated return type is `EventEmitter`.

`typechain --target=web3-v1` generates this:
```typescript
export interface MyContract extends BaseContract {
events: {
SomeEvent(cb?: Callback): EventEmitter;
}
}
```
...but should generate this:
```typescript
export interface MyContract extends BaseContract {
events: {
SomeEvent(cb?: Callback): Subscription; // <--- different return type
}
}
```