E2E test: don't override image.tag for agent

qa/qa/runtime/env.rb

@@ -574,10 +574,6 @@ def geo_environment?
         QA::Runtime::Scenario.attributes.include?(:geo_secondary_address)
       end
 
-      def gitlab_agentk_version
-        ENV.fetch('GITLAB_AGENTK_VERSION', 'latest')
-      end
-
       def transient_trials
         ENV.fetch('GITLAB_QA_TRANSIENT_TRIALS', 10).to_i
       end

qa/qa/service/cluster_provider/gcloud.rb

@@ -50,7 +50,6 @@ def install_kubernetes_agent(agent_token:, kas_address:, agent_name: "gitlab-age
             helm upgrade --install gitlab-agent gitlab/gitlab-agent
               --namespace "#{agent_name}"
               --create-namespace
-              --set image.tag=#{Runtime::Env.gitlab_agentk_version}
               --set config.token=#{agent_token}
               --set config.kasAddress=#{kas_address}
               --set config.kasHeaders="{Cookie: gitlab_canary=#{target_canary?}}"