[vscode-graphql] use of fragment variable in template string breaks autocomplete

The following works fine and the autocomplete works as expected:

```js
const query = /* GraphQL */ `
query GetItem($name: String!) {
getItem(name: $name) {
id
}
}
`;
```

But when it is changed to the following, the autocomplete breaks:

```js
const fragment = /* GraphQL */ `
fragment PartialItem on Item {
name
age
job
}
`

const query = /* GraphQL */ `
${fragment}
query GetItem($name: String!) {
getItem(name: $name) {
id
...PartialItem
}
}
`;
```

What I've figured out so far:

* If the fragment is in-lined in the query, it works as expected. So it is due to it being a separate variable.
* Actually using the fragment in the query is not needed to break it. Simply adding `${fragment}` is all that is needed to break it.
* When "broken" the auto complete will always suggest the same options as if the entire template string was empty.