`template` doesn't impact output for some fields

We have a file `.grenrc.js` generated from `gren int`

After adding a template object it looks like this:

```
module.exports = {
"dataSource": "milestones",
"prefix": "n",
"groupBy": "label",
"milestoneMatch": "{{tag_name}}",
"changelogFilename": "CHANGELOG.md",
"template": {
commit: ({ message, url, author, name }) => `- [${message}](${url}) - ${author ? `@${author}` : name}`,
issue: "- {{labels}} {{name}} [{{text}}]({{url}})",
label: "[**{{label}}**]",
noLabel: "closed",
group: "\n#### {{heading}}\n",
changelogTitle: "# Changelog\n\n",
release: "## {{release}} ({{date}})\n{{body}}",
releaseSeparator: "\n---\n\n"
}
}
```

When I change values for `issue`, `label` or `group`, the `CHANGELOG.md` file is still generated from the original template. Changing values for `release` and `changelogTitle` do impact though.

Reproduce the issue with the generated .grenrc.js and inspect how its template values are applied when generating CHANGELOG.md. Compare the handling of issue, label, and group with release and changelogTitle, then verify that changing each value changes the corresponding output.

Written by the indexing model from the issue text.