fix: remove the update lock after a successful update with macOS

[brandonskiser]

Description of changes:

• Currently, when a user auto-updates into the latest version of q, we advertise updating into kiro. Since the update lockfile is not cleaned up on macOS after a successful update, this results in an error about "update in progress" until an hour has passed.
• Removing the lockfile after a successful update. Note that if we are updating the lockfile path between versions (q -> kiro), then the kiro finish update won't remove the q update lockfile. This is fine though, since the old lockfile won't be used anyways.

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