Add default value to database column list_user_preferences.collapsed

What does this MR do?

Add a default FALSE not null constraint to list_user_preferences.collapsed database column.

This change is to make data structure consistent between the list_user_preferences table and boards_epic_list_user_preferences which share common code on the application.

Migration output

== 20210415180356 AddCollapsedDefaultValueToListUserPreferences: migrating ====
-- change_column_default(:list_user_preferences, :collapsed, {:from=>nil, :to=>false})
   -> 0.0036s
-- change_column_null(:list_user_preferences, :collapsed, false)
   -> 0.0017s
== 20210415180356 AddCollapsedDefaultValueToListUserPreferences: migrated (0.0054s)