Fix preloading of deployments

app/serializers/environment_serializer.rb

@@ -60,7 +60,7 @@ class EnvironmentSerializer < BaseSerializer
     Preloaders::Environments::DeploymentPreloader.new(resource)
       .execute_with_union(:upcoming_deployment, deployment_associations)
 
-    resource.all.to_a.tap do |environments|
+    resource.to_a.tap do |environments|
       environments.each do |environment|
         # Batch loading the commits of the deployments
         environment.last_deployment&.commit&.try(:lazy_author)

spec/support/shared_examples/serializers/environment_serializer_shared_examples.rb

 # frozen_string_literal: true
 RSpec.shared_examples 'avoid N+1 on environments serialization' do |ee: false|
   # Investigating in https://gitlab.com/gitlab-org/gitlab/-/issues/353209
-  let(:query_threshold) { 50 + (ee ? 4 : 0) }
+  let(:query_threshold) { 9 + (ee ? 4 : 0) }
 
   it 'avoids N+1 database queries with grouping', :request_store do
     create_environment_with_associations(project)