Enable notification settings in menu

[google-labs-jules]

Enable "Show Message Preview" and "Show Notifications" in menu

Removed the is.development visibility flag from "Show Message Preview" and "Show Notifications" menu items as the underlying logic has been fixed. Also removed a duplicate "Show Message Preview in Notifications" item.

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PR created automatically by Jules for task 10027553791098758557 started by @raztronaut

[google-labs-jules]

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