`update_existing` doesn't match title with `{{mustache}}`

Hello,

Pretty much as the title. I have the following template:
```md
---
title: "({{env.TARGET_ENV}}) The {{env.RELEASE_NAME}} Release has failed. :scream_cat:"
labels: failed-release
---
See https://github.com/{{tools.context.issue}}/actions/runs/{{env.GITHUB_RUN_ID}}
```

The action doesn't match an issue with **the same title**.