Maintenance: Custom rubocops should inherit from Base not Cop (as other core rubocops).

.rubocop/cop/zammad/exists_condition.rb

@@ -20,7 +20,7 @@ module RuboCop
       #   if exists?(name: 'Rubocop')
       #   if !exists?(name: 'Rubocop')
       #   unless exists?(name: 'Rubocop')
-      class ExistsCondition < Cop
+      class ExistsCondition < Base
 
         def_node_matcher :find_by_condition?, <<-PATTERN
           {

.rubocop/cop/zammad/prefer_negated_if_over_unless.rb

@@ -11,7 +11,7 @@ module RuboCop
       #   # good
       #   if !statement
       #   return if !statement
-      class PreferNegatedIfOverUnless < Cop
+      class PreferNegatedIfOverUnless < Base
         include ConfigurableEnforcedStyle
         include NegativeConditional
         extend AutoCorrector