Remove fallback to DEL, since we no longer support redis 3

ee/lib/gitlab/elastic/elasticsearch_enabled_cache.rb

@@ -55,9 +55,7 @@ module Gitlab
         #
         # @param type [Symbol] the type of resource, `:project` or `:namespace`
         def delete(type)
-          Gitlab::Redis::Cache.with do |redis|
-            unlink_or_delete(redis, redis_key(type))
-          end
+          Gitlab::Redis::Cache.with { |redis| redis.unlink(redis_key(type)) }
         end
 
         private
@@ -65,13 +63,6 @@ module Gitlab
         def redis_key(type)
           "elasticsearch_enabled_cache:#{type}"
         end
-
-        def unlink_or_delete(redis, key)
-          redis.unlink(key)
-        rescue ::Redis::CommandError => e
-          Gitlab::ErrorTracking.log_exception(e)
-          redis.del(key)
-        end
       end
     end
   end