Fix: Enable previously skipped Playwright crypto test for 'gray shields'

[BillCarsonFr]

Fixes element-hq/element-web#26811

The test was incorrectly testing for the presence of a red shield. It was probably expecting a Message sent from a deleted device.
In that case it is true that the sending device is deleted, but the key is coming from the backup. At the moment keys coming from backup can't be linked back to the device that created them (until authenticated backup is implemented).
That's why the shield would be gray. If we can't establish authenticity, we can't make any checks on the device (is signed by it's owner? verified by us? is it deleted?)

Checklist

• Tests written for new code (and old code if feasible)
• Linter and other CI checks pass
• Sign-off given on the changes (see CONTRIBUTING.md)

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This change is marked as an internal change (Task), so will not be included in the changelog.