Non payable message in Ask! ?

In Ask! message is payable even if there's no modifiers.
For example,
```
@message({ mutates: true })
flip(): void {
this.data.flag = !this.data.flag;
let event = new FlipEvent(this.data.flag);
// @ts-ignore
env().emitEvent(event);
}
```
This will generate metadata.json payable true, and it is actually payable.
```
"messages": [
{
"mutates": true,
"payable": true,
"args": [],
"docs": [],
"label": "flip",
"selector": "0x633aa551"
}
]
```

Is there a way to specify message to be non-payable?

Start with the `@message` example and the generated `metadata.json` shown in the issue; determine how message modifiers currently affect the `payable` metadata. The issue asks whether messages can be made non-payable, so done means establishing a supported way to express that and verifying the generated metadata reflects it.

Written by the indexing model from the issue text.