Fix broken review-cleanup job

The automated clean up job required ruby 3.0.0.
However, the image with ruby 3.0.0 does not contain
`gcloud`, which is also needed in the job.

This changes the script to be compatible with
ruby that is lower than 3.0.0 and reverts the image used.

.gitlab/ci/review.gitlab-ci.yml

@@ -2,7 +2,7 @@ review-cleanup:
   extends:
     - .default-retry
     - .review:rules:review-cleanup
-  image: registry.gitlab.com/gitlab-org/gitlab-build-images:gitlab-helm3.5-kubectl1.17
+  image: registry.gitlab.com/gitlab-org/gitlab-build-images:gitlab-helm3-kubectl1.14
   stage: prepare
   environment:
     name: review/auto-cleanup

tooling/lib/tooling/kubernetes_client.rb

@@ -142,10 +142,13 @@ module Tooling
     def resources_created_before_date(response, date)
       items = JSON.parse(response)['items'] # rubocop:disable Gitlab/Json
 
-      items.filter_map do |item|
+      items.each_with_object([]) do |item, result|
         item_created_at = Time.parse(item.dig('metadata', 'creationTimestamp'))
 
-        item.dig('metadata', 'name') if item_created_at < date
+        if item_created_at < date
+          resource_name = item.dig('metadata', 'name')
+          result << resource_name
+        end
       end
     rescue ::JSON::ParserError => ex
       puts "Ignoring this JSON parsing error: #{ex}\n\nResponse was:\n#{response}" # rubocop:disable Rails/Output