Remove unused logic for whether a zone is "sometimes" occupied

I'm about to reimplement the more-robust version of what this used to
be: how the item page used to say "sometimes" after certain zones in
the occupied list.

Now, we're going to do parity with 2020, and list the actual species!

I like that this takes away the weird `#sometimes` method on the `Zone`
class, which was always an odd hack for just this small thing.

app/models/item.rb

@@ -283,23 +283,9 @@ class Item < ApplicationRecord
     occupied_zones.map(&:id)
   end
 
-  def occupied_zones(options={})
-    options[:scope] ||= Zone.all
-    all_body_ids = []
-    zone_body_ids = {}
-    selected_assets = swf_assets.each do |swf_asset|
-      zone_body_ids[swf_asset.zone_id] ||= []
-      body_ids = zone_body_ids[swf_asset.zone_id]
-      body_ids << swf_asset.body_id unless body_ids.include?(swf_asset.body_id)
-      all_body_ids << swf_asset.body_id unless all_body_ids.include?(swf_asset.body_id)
-    end
-    zones = options[:scope].find(zone_body_ids.keys)
-    zones_by_id = zones.inject({}) { |h, z| h[z.id] = z; h }
-    total_body_ids = all_body_ids.size
-    zone_body_ids.each do |zone_id, body_ids|
-      zones_by_id[zone_id].sometimes = true if body_ids.size < total_body_ids
-    end
-    zones
+  def occupied_zones
+    zone_ids = swf_assets.map(&:zone_id).uniq
+    Zone.find(zone_ids)
   end
 
   def affected_zones

app/models/zone.rb

@@ -1,8 +1,4 @@
 class Zone < ActiveRecord::Base
-  # When selecting zones that an asset occupies, we allow the zone to set
-  # whether or not the zone is "sometimes" occupied. This is false by default.
-  attr_writer :sometimes
-  
   scope :alphabetical, -> { order(:label) }
   scope :matching_label, ->(label) {
     where(plain_label: Zone.plainify_label(label))
@@ -13,10 +9,6 @@ class Zone < ActiveRecord::Base
     super({only: [:id, :depth, :label]}.merge(options))
   end
 
-  def uncertain_label
-    @sometimes ? "#{label} sometimes" : label
-  end
-
   def is_commonly_used_by_items
     # Zone metadata marks item zones with types 2, 3, and 4. But also, in
     # practice, the Biology Effects zone (type 1, ID 4) has been used for a few