Remove unnecessary tag rule code

The applicator converts the input to an array, even `nil` becomes an
empty array. Iterating over an empty array doesn't do anything either,
the result is the same.

lib/open_food_network/tag_rule_applicator.rb

@@ -14,8 +14,6 @@ module OpenFoodNetwork
     end
 
     def filter!(subject)
-      return unless subject.respond_to?(:any?) && subject.any?
-
       subject.to_a.reject! do |element|
         if rule_class.respond_to?(:tagged_children_for)
           children = rule_class.tagged_children_for(element)