DEV: Drop `show_filter_by_tag` site settings.

Follow-up to 83519e7f3a

db/migrate/20210311022303_drop_show_filter_by_tag_site_setting.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+class DropShowFilterByTagSiteSetting < ActiveRecord::Migration[6.0]
+  def up
+    execute <<~SQL
+      DELETE FROM site_settings
+      WHERE name = 'show_filter_by_tag'
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end