ci: Use MetaMask/action-is-release@v2 for release check workflow (#7158)

## Explanation

The changes needed for the release check are now included in the stable
version of `MetaMask/action-is-release`, so we can use that instead.

## References

<!--
Are there any issues that this pull request is tied to?
Are there other links that reviewers should consult to understand these
changes better?
Are there client or consumer pull requests to adopt any breaking
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* Fixes #12345
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## Checklist

- [ ] I've updated the test suite for new or updated code as appropriate
- [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [ ] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Update workflow to use `MetaMask/action-is-release@v2` instead of a
pinned commit for release detection.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
b7c4a07. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: Mrtenz

.github/workflows/main.yml

@@ -84,7 +84,7 @@ jobs:
       - name: Check if the commit or pull request is a release
         id: is-release
         if: github.event_name != 'push'
-        uses: MetaMask/action-is-release@d063725cd15ee145d7e795a2e77db31a3e3f2c92
+        uses: MetaMask/action-is-release@v2
         with:
           commit-starts-with: 'Release [version],Release v[version],Release/[version],Release/v[version],Release `[version]`'
           commit-message: ${{ github.event.pull_request.title }}