Wrong highlighting for function that splits over multiple lines inside a string

Originally reported in https://github.com/hashicorp/vscode-terraform/issues/1756

## Example

```hcl
locals {
list = [
"1", "2", "3"
]
function = [
for i in local.list : "Out: ${join("-", [i, "join"]
)}" if i != "2"
]
}

output "test" {
value = local.function
}
```


It breaks some time after the [0.4.2](https://github.com/hashicorp/syntax/releases/tag/v0.4.2) release