Add expiry to feedback badge

We should limit the duration of the "New look" badge to reduce noise as it's non-dismissible. While this means users installing the "new" version later will not see it, this is preferable vs. having it be visible indefinitely until upgrade (on self-managed).

Acceptance criteria:

• "New look" badge appears for 1 week
  • Using date-based expiry, this would be 1 week after the 17.11 release date