Bump dessant/lock-threads from 3 to 4 (#777)

Bumps [dessant/lock-threads](https://github.com/dessant/lock-threads) from 3 to 4.
- [Release notes](https://github.com/dessant/lock-threads/releases)
- [Changelog](https://github.com/dessant/lock-threads/blob/master/CHANGELOG.md)
- [Commits](dessant/lock-threads@v3...v4)

---
updated-dependencies:
- dependency-name: dessant/lock-threads
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/lock.yml

@@ -11,7 +11,7 @@ jobs:
     if: github.repository_owner == 'pyca'
     runs-on: ubuntu-latest
     steps:
-      - uses: dessant/lock-threads@v3
+      - uses: dessant/lock-threads@v4
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           issue-inactive-days: 90