Remove use_work_items_view column from user_preferences

What does this MR do and why?

Drops the use_work_items_view column from user_preferences. The column was already ignored in the model in !256130 (merged), and all application code referencing it was removed there. This MR is the second step of the three-release column removal process (ignore -> drop -> remove ignore rule).

References

Resolves #550770 Depends on !256130 (merged)

How to set up and validate locally

1. Check out this branch and run bundle exec rake db:migrate.
2. Confirm the use_work_items_view column no longer exists on user_preferences:

   ActiveRecord::Base.connection.column_exists?(:user_preferences, :use_work_items_view)
   # => false

MR acceptance checklist

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