chore: prevent actions from running on forks

[alessbell]

I've noticed a couple of PRs automatically opened on forks due to the release workflow running. They're harmless insofar as merging them will do nothing (the action will fail), but they create noise and waste resources.

prerelease.yml already had this if condition that checks the repository name, so I've added it to release.yml and also close-stale-issues.yml (again, probably harmless if it runs but makes no sense to run on forks).

Checklist:

• If this PR contains changes to the library itself (not necessary for e.g. docs updates), please include a changeset (see CONTRIBUTING.md)
• If this PR is a new feature, please reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests

[changeset-bot]

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Latest commit: ba3dacd

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