[Swift 6 Migration] [UI Tests] Fix nonisolated(unsafe) global springboard buttons vars in TodayWidgetTests.swift

[data-sync-user]

nonisolated(unsafe) static var corruptionLogsWritten = Set<String>()

These are global properties, and because they are mutable they are not thread safe.

However, since these are in UI tests the risk is low.

Also, it could be that the risk is zero due to how tests run (individually per device?). But we should double check just in case.

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